The 20th century British scientist Sir James Jeans wrote that "the Universe begins to look more like a great thought than like a great machine"

In philosophy, idealism is the group of philosophies which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing. In a sociological sense, idealism emphasizes how human ideas — especially beliefs and values — shape society. ^[1] As an ontological doctrine, idealism goes further, asserting that all entities are composed of mind or spirit.^[2] Idealism thus rejects physicalist and dualist theories that fail to ascribe priority to the mind. An extreme version of this idealism can exist in the philosophical notion of solipsism.

Religious and philosophical thought privileging the immaterial or supernatural over the material and natural is ubiquitous and ancient. However, the earliest extant arguments that the world of experience is grounded in the mental derive from India and Greece. The Hindu idealists in India and the Greek Neoplatonists gave pantheistic arguments for an all-pervading consciousness as the ground or true nature of reality.^[3] In contrast, the Yogācāra school, which arose within Mahayana Buddhism in India in the 4th century CE,^[4] based its "mind-only" idealism to a greater extent on phenomenological analyses of personal experience. This turn toward the subjective anticipated empiricists such as George Berkeley, who revived idealism in 18th-century Europe by employing skeptical arguments against materialism.

Beginning with Immanuel Kant, German idealists such as G. W. F. Hegel, Johann Gottlieb Fichte, Friedrich Wilhelm Joseph Schelling, and Arthur Schopenhauer dominated 19th-century philosophy. This tradition, which emphasized the mental or "ideal" character of all phenomena, birthed idealistic and subjectivist schools ranging from British idealism to phenomenalism to existentialism. The historical influence of this branch of idealism remains central even to the schools that rejected its metaphysical assumptions, such as Marxism, pragmatism, and positivism.

Definitions[link]

Idealism is a term with several related meanings. It comes via idea from the Greek idein (ἰδεῖν), meaning "to see". The term entered the English language by 1796. In ordinary use, as when speaking of Woodrow Wilson's political idealism, it generally suggests the priority of ideals, principles, values, and goals over concrete realities. Idealists are understood to represent the world as it might or should be, unlike pragmatists, who focus on the world as it presently is. In the arts, similarly, idealism affirms imagination and attempts to realize a mental conception of beauty, a standard of perfection, in opposition to aesthetic naturalism and realism.^[5][6]

Any philosophy that assigns crucial importance to the ideal or spiritual realm in its account of human existence may be termed "idealist". Metaphysical idealism is an ontological doctrine that holds that reality itself is incorporeal or experiential at its core. Beyond this, idealists disagree on which aspects of the mental are more basic. Platonic idealism affirms that abstractions are more basic to reality than the things we perceive, while subjective idealists and phenomenalists tend to privilege sensory experience over abstract reasoning. Epistemological idealism is the weaker view that reality can only be known through ideas, that only psychological experience can be apprehended by the mind.^[2][7][8]

Subjective idealists like George Berkeley are anti-realists in terms of a mind-independent world, whereas transcendental idealists like Immanuel Kant are strong skeptics of such a world, affirming epistemological and not metaphysical idealism. Thus Kant defines idealism as "the assertion that we can never be certain whether all of our putative outer experience is not mere imagining".^[9] However, not all idealists restrict the real or the knowable to our immediate subjective experience. Objective idealists make claims about a transempirical world, but simply deny that this world is essentially divorced from or ontologically prior to the mental. Thus Plato and Gottfried Leibniz affirm an objective and knowable reality transcending our subjective awareness—a rejection of epistemological idealism—but propose that this reality is grounded in ideal entities, a form of metaphysical idealism. Nor do all metaphysical idealists agree on the nature of the ideal; for Plato, the fundamental entities were non-mental abstract forms, while for Leibniz they were proto-mental and concrete monads.^[10]

As a rule, transcendental idealists like Kant affirm idealism's epistemic side without committing themselves to whether reality is ultimately mental; objective idealists like Plato affirm reality's metaphysical basis in the mental or abstract without restricting their epistemology to ordinary experience; and subjective idealists like Berkeley affirm both metaphysical and epistemological idealism.^[11]

Classical idealism[link]

Monistic idealism holds that consciousness, not matter, is the ground of all being. It is monist because it holds that there is only one type of thing in the universe and idealist because it holds that one thing to be consciousness.

Anaxagoras (480 BC) was known as "Nous" ("Mind") because he taught that "all things" were created by Mind, that Mind held the cosmos together and gave human beings a connection to the cosmos or a pathway to the divine.

Many religious philosophies are specifically idealist. The belief that beings with knowledge (God/s, angels & spirits) preceded insentient matter seems to suggest that an experiencing subject is a necessary reality. Hindu idealism is central to Vedanta philosophy and to such schools as Kashmir Shaivism.^[12] Proponents include Amit Goswami,^[13] P.R. Sarkar and his disciple Sohail Inayatullah.

Christian theologians have held idealist views, often based on Neoplatonism, despite the influence of Aristotelian scholasticism from the 12th century onward. Later western theistic idealism such as that of Hermann Lotze offers a theory of the "world ground" in which all things find their unity: it has been widely accepted by Protestant theologians.^[14] Several modern religious movements, for example the organizations within the New Thought Movement and the Unity Church, may be said to have a particularly idealist orientation. The theology of Christian Science includes a form of idealism: it teaches that all that truly exists is God and God's ideas; that the world as it appears to the senses is a distortion of the underlying spiritual reality, a distortion that may be corrected (both conceptually and in terms of human experience) through a reorientation (spiritualization) of thought.

Wang Yangming, a Ming Chinese neo-Confucian philosopher, official, educationist, calligraphist and general, held that objects do not exist entirely apart from the mind because the mind shapes them. It is not the world that shapes the mind but the mind that gives reason to the world, so the mind alone is the source of all reason, having an inner light, an innate moral goodness and understanding of what is good.

The consciousness-only approach of the Yogācāra school of Mahayana Buddhism is not true metaphysical idealism^[15] as Yogācāra thinkers did not focus on consciousness to assert it as ultimately real, it is only conventionally real since it arises from moment to moment due to fluctuating causes and conditions and is significant because it is the cause of karma and hence suffering.^[16]

In recent years, a form of monistic idealism has been defended by the physicist Amit Goswami:^{[17][18][19][20]}

The current worldview has it that everything is made of matter, and everything can be reduced to the elementary particles of matter, the basic constituents — building blocks — of matter. And cause arises from the interactions of these basic building blocks or elementary particles; elementary particles make atoms, atoms make molecules, molecules make cells, and cells make brain. But all the way, the ultimate cause is always the interactions between the elementary particles. This is the belief — all cause moves from the elementary particles. This is what we call "upward causation." So in this view, what human beings — you and I think of as our free will does not really exist. It is only an epiphenomenon or secondary phenomenon, secondary to the causal power of matter. And any causal power that we seem to be able to exert on matter is just an illusion. This is the current paradigm.
Now, the opposite view is that everything starts with consciousness. That is, consciousness is the ground of all being. In this view, consciousness imposes "downward causation." In other words, our free will is real. When we act in the world we really are acting with causal power. This view does not deny that matter also has causal potency — it does not deny that there is causal power from elementary particles upward, so there is upward causation — but in addition it insists that there is also downward causation. It shows up in our creativity and acts of free will, or when we make moral decisions. In those occasions we are actually witnessing downward causation by consciousness.

Platonism and neoplatonism[link]

Plato's theory of forms or "ideas" describes ideal forms (for example the platonic solids in geometry or abstracts like Goodness and Justice), as universals existing independently of any particular instance.^[21] Arne Grøn calls this doctrine "the classic example of a metaphysical idealism as a transcendent idealism",^[22] while Simone Klein calls Plato "the earliest representative of metaphysical objective idealism". Nevertheless Plato holds that matter is real, though transitory and imperfect, and is perceived by our body and its senses and given existence by the eternal ideas that are perceived directly by our rational soul. Plato was therefore a metaphysical and epistemological dualist, an outlook that modern idealism has striven to avoid:^[23] Plato's thought cannot therefore be counted as idealist in the modern sense.

With the neoplatonist Plotinus, wrote Nathaniel Alfred Boll; "there even appears, probably for the first time in Western philosophy, idealism that had long been current in the East even at that time, for it taught… that the soul has made the world by stepping from eternity into time…".^[24][25] Similarly, in regard to passages from the Enneads, "The only space or place of the world is the soul" and "Time must not be assumed to exist outside the soul",^[26] Ludwig Noiré wrote: "For the first time in Western philosophy we find idealism proper in Plotinus,^[3] However, Plotinus does not address whether we know external objects, unlike Schopenhauer and other modern philosophers.

Subjective idealism[link]

Subjective Idealism (immaterialism or phenomenalism) describes a relationship between experience and the world in which objects are no more than collections or "bundles" of sense data in the perceiver. Proponents include Berkeley,^[27] Bishop of Cloyne, an Irish philosopher who advanced a theory he called immaterialism, later referred to as "subjective idealism", contending that individuals can only know sensations and ideas of objects directly, not abstractions such as "matter", and that ideas also depend upon being perceived for their very existence - esse est percipi; "to be is to be perceived".

Arthur Collier^[28] published similar assertions though there seems to have been no influence between the two contemporary writers. The only knowable reality is the represented image of an external object. Matter as a cause of that image, is unthinkable and therefore nothing to us. An external world as absolute matter unrelated to an observer does not exist as far as we are concerned. The universe cannot exist as it appears if there is no perceiving mind. Collier was influenced by An Essay Towards the Theory of the Ideal or Intelligible World by "Cambridge Platonist" John Norris (1701).

Bertrand Russell's popular book The Problems of Philosophy highlights Berkeley's tautological premise for advancing idealism;

"If we say that the things known must be in the mind, we are either un-duly limiting the mind's power of knowing, or we are uttering a mere tautology. We are uttering a mere tautology if we mean by 'in the mind' the same as by 'before the mind', i.e. if we mean merely being apprehended by the mind. But if we mean this, we shall have to admit that what, in this sense, is in the mind, may nevertheless be not mental. Thus when we realize the nature of knowledge, Berkeley's argument is seen to be wrong in substance as well as in form, and his grounds for supposing that 'idea'-i.e. the objects apprehended-must be mental, are found to have no validity whatever. Hence his grounds in favour of the idealism may be dismissed."

The Australian philosopher David Stove harshly criticized philosophical idealism, arguing that it rests on what he called "the worst argument in the world". Stove claims that Berkeley tried to derive a non-tautological conclusion from tautological reasoning. He argued that in Berkeley's case the fallacy is not obvious and this is because one premise is ambiguous between one meaning which is tautological and another which, Stove argues, is logically equivalent to the conclusion.

Alan Musgrave^[29] argues that conceptual idealists compound their mistakes with use/mention confusions;

Santa Claus the person does not exist.

"Santa Claus" the name/concept/fairy tale does exist because adults tell children this every Christmas season (the distinction is highlighted by using quotation-marks when referring only to the name and not the object)

and proliferation of hyphenated entities such as "thing-in-itself" (Immanuel Kant), "things-as-interacted-by-us" (Arthur Fine), "table-of-commonsense" and "table-of-physics" (Sir Arthur Eddington) which are "warning signs" for conceptual idealism according to Musgrave because they allegedly do not exist but only highlight the numerous ways in which people come to know the world. This argument does not take into account the issues pertaining to hermeneutics, especially at the backdrop of analytic philosophy. Musgrave criticized Richard Rorty and Postmodernist philosophy in general for confusion of use and mention.

A. A. Luce^[30] and John Foster are other subjectivists.^[31] Luce, in Sense without Matter (1954), attempts to bring Berkeley up to date by modernising his vocabulary and putting the issues he faced in modern terms, and treats the Biblical account of matter and the psychology of perception and nature. Foster's The Case for Idealism argues that the physical world is the logical creation of natural, non-logical constraints on human sense-experience. Foster's latest defence of his views is in his book A World for Us: The Case for Phenomenalistic Idealism.

Paul Brunton, a British philosopher, mystic, traveler, and guru, taught a type of idealism called "mentalism", similar to that of Bishop Berkeley, proposing a master world-image, projected or manifested by a world-mind, and an infinite number of individual minds participating. A tree does not cease to exist if nobody sees it because the world-mind is projecting the idea of the tree to all minds.^[32]

John Searle criticising some versions of idealism, summarises two important arguments for subjective idealism. The first is based on our perception of reality;

(1) All we have access to in perception are the contents of our own experience and

(2) The only epistemic basis for claims about the external world are our perceptual experiences

therefore;

(3) The only reality we can meaningfully speak of is that of perceptual experience ^[33]

Whilst agreeing with (2) Searle argues that (1) is false and points out that (3) does not follow from (1) and (2). The second argument runs as follows;

Premise: Any cognitive state occurs as part of a set of cognitive states and within a cognitive system

Conclusion 1: It is impossible to get outside all cognitive states and systems to survey the relationships between them and the reality they cognize

Conclusion 2: There is no cognition of any reality that exists independently of cognition^[34]

Searle contends that Conclusion 2 does not follow from the premises.

Epistemological idealism is a subjectivist position in epistemology that holds that what one knows about an object exists only in one's mind. Proponents include Brand Blanshard.

Transcendental idealism[link]

Transcendental idealism, founded by Immanuel Kant in the eighteenth century, maintains that the mind shapes the world we perceive into the form of space-and-time.

... if I remove the thinking subject, the whole material world must at once vanish because it is nothing but a phenomenal appearance in the sensibility of ourselves as a subject, and a manner or species of representation.

— Critique of Pure Reason A383

The 2nd edition (1787) contained a Refutation of Idealism to distinguish his transcendental idealism from Descartes's Sceptical Idealism and Berkeley's Dogmatic Idealism. The section Paralogisms of Pure Reason is an implicit critique of Descartes' idealism. Kant says that it is not possible to infer the 'I' as an object (Descartes' Cogito ergo sum) purely from "the spontaneity of thought". Kant focused on ideas drawn from British philosophers such as Locke, Berkeley and Hume but distinguished his transcendental or critical idealism from previous varieties;

The dictum of all genuine idealists, from the Eleatic school to Bishop Berkeley, is contained in this formula: “All knowledge through the senses and experience is nothing but sheer illusion, and only in the ideas of the pure understanding and reason is there truth.” The principle that throughout dominates and determines my [transcendental] idealism is, on the contrary: “All knowledge of things merely from pure understanding or pure reason is nothing but sheer illusion, and only in experience is there truth.”

— Prolegomena, 374

Kant distinguished things as they appear to an observer and things in themselves, "that is, things considered without regard to whether and how they may be given to us".^[35] We cannot approach the noumenon, the "thing in Itself" (German: Ding an sich) without our own mental world. He added that the mind is not a blank slate, tabula rasa but rather comes equipped with categories for organising our sense impressions.

In the first volume of his Parerga and Paralipomena, Schopenhauer wrote his "Sketch of a History of the Doctrine of the Ideal and the Real". He defined the ideal as being mental pictures that constitute subjective knowledge. The ideal, for him, is what can be attributed to our own minds. The images in our head are what comprise the ideal. Schopenhauer emphasized that we are restricted to our own consciousness. The world that appears is only a representation or mental picture of objects. We directly and immediately know only representations. All objects that are external to the mind are known indirectly through the mediation of our mind. He offered a history of the concept of the "ideal" as "ideational" or "existing in the mind as an image".

[T]rue philosophy must at all costs be idealistic; indeed, it must be so merely to be honest. For nothing is more certain than that no one ever came out of himself in order to identify himself immediately with things different from him; but everything of which he has certain, sure, and therefore immediate knowledge, lies within his consciousness. Beyond this consciousness, therefore, there can be no immediate certainty ... There can never be an existence that is objective absolutely and in itself; such an existence, indeed, is positively inconceivable. For the objective, as such, always and essentially has its existence in the consciousness of a subject; it is therefore the subject's representation, and consequently is conditioned by the subject, and moreover by the subject's forms of representation, which belong to the subject and not to the object.

— The World as Will and Representation, Vol. II, Ch. 1

Charles Bernard Renouvier was the first Frenchman after Nicolas Malebranche to formulate a complete idealistic system, and had a vast influence on the development of French thought. His system is based on Immanuel Kant's, as his chosen term "néo-criticisme" indicates; but it is a transformation rather than a continuation of Kantianism.

Friedrich Nietzsche argued that Kant confuses tautology and petitio principii, and ridicules his pride in tackling "the most difficult thing that could ever be undertaken on behalf of metaphysics.".^[36] Yet he attacks the idealism of Schopenhauer and Descartes with an argument similar to Kant's critique of the latter (see above);

Objective idealism[link]

Objective idealism asserts that the reality of experiencing combines and transcends the realities of the object experienced and of the mind of the observer.^[37] Proponents include Thomas Hill Green, Josiah Royce, Benedetto Croce and Charles Sanders Peirce.^[38]

Absolute idealism[link]

Johann Fichte was the first German philosopher to make an attempt at a presuppositionless theory of knowledge, wherein nothing outside of thought is assumed to exist apart from the primordial analysis of the Ego. So that his philosophy could be solely grounded in itself, he assumed nothing without his Fichtean deductions from first principles, and elaborated what he called a Wissenschaftslehre. Fichte denied Kant's noumenon and held that consciousness constitutes its own foundation, that the mental life of the Ego, of pure selfhood, relies upon nothing wholly external to itself and that the hypothesis of an outer world of any kind is the same thing as admitting a Kantian realm.

Schelling (1775–1854) claimed that the Fichte's "I" needs the Not-I, because there is no subject without object, and vice versa. So there is no difference between the subjective and the objective, that is, the ideal and the real. This is Schelling's "absolute identity": the ideas or mental images in the mind are identical to the extended objects which are external to the mind.

Absolute idealism is G. W. F. Hegel's account of how existence is comprehensible as an all-inclusive whole. Hegel called his philosophy "absolute" idealism in contrast to the "subjective idealism" of Berkeley and the "transcendental idealism" of Kant and Fichte,^[39] which were not based on a critique of the finite and a dialectical philosophy of history as Hegel's idealism was. The exercise of reason and intellect enables the philosopher to know ultimate historical reality, the phenomenological constitution of self-determination, the dialectical development of self-awareness and personality in the realm of History.

In his Science of Logic (1812–1814) Hegel argues that finite qualities are not fully "real" because they depend on other finite qualities to determine them. Qualitative infinity, on the other hand, would be more self-determining and hence more fully real. Similarly finite natural things are less "real"—because they are less self-determining—than spiritual things like morally responsible people, ethical communities and God. So any doctrine, such as materialism, that asserts that finite qualities or natural objects are fully real is mistaken.^[40]

Hegel certainly intends to preserve what he takes to be true of German idealism, in particular Kant's insistence that ethical reason can and does go beyond finite inclinations.^[41] For Hegel there must be some identity of thought and being for the subject (human reason or consciousness) to be able to know an object (the world) at all.

Kierkegaard criticised Hegel's idealist philosophy in several of his works, particularly his claim to a comprehensive system that could explain the whole of reality. Where Hegel argues that an ultimate understanding of the logical structure of the world is an understanding of the logical structure of God's mind, Kierkegaard asserting that for God reality can be a system but it cannot be so for any human individual because both reality and humans are incomplete and all philosophical systems imply completeness. A logical system is possible but an existential system is not. "What is rational is actual; and what is actual is rational".^[42] Hegel's absolute idealism blurs the distinction between existence and thought: our mortal nature places limits on our understanding of reality;

So-called systems have often been characterized and challenged in the assertion that they abrogate the distinction between good and evil, and destroy freedom. Perhaps one would express oneself quite as definitely, if one said that every such system fantastically dissipates the concept existence. ... Being an individual man is a thing that has been abolished, and every speculative philosopher confuses himself with humanity at large; whereby he becomes something infinitely great, and at the same time nothing at all.

^[43]

A major concern of Hegel's Phenomenology of Spirit (1807) and of the philosophy of Spirit that he lays out in his Encyclopedia of the Philosophical Sciences (1817–1830) is the interrelation between individual humans, which he conceives in terms of "mutual recognition." However, what Climacus means by the aforementioned statement, is that Hegel, in the Philosophy of Right, believed the best solution was to surrender one's individuality to the customs of the State, identifying right and wrong in view of the prevailing bourgeois morality. Individual human will ought, at the State's highest level of development, to properly coincide with the will of the State. Climacus rejects Hegel's suppression of individuality by pointing out it is impossible to create a valid set of rules or system in any society which can adequately describe existence for any one individual. Submitting one's will to the State denies personal freedom, choice, and responsibility.

In addition, Hegel does believe we can know the structure of God's mind, or ultimate reality. Hegel agrees with Kierkegaard that both reality and humans are incomplete, inasmuch as we are in time, and reality develops through time. But the relation between time and eternity is outside time and this is the "logical structure" that Hegel thinks we can know. Kierkegaard disputes this assertion, because it eliminates the clear distinction between ontology and epistemology. Existence and thought are not identical and one cannot possibly think existence. Thought is always a form of abstraction, and thus not only is pure existence impossible to think, but all forms in existence are unthinkable; thought depends on language, which merely abstracts from experience, thus separating us from lived experience and the living essence of all beings. In addition, because we are finite beings, we cannot possibly know or understand anything that is universal or infinite such as God, so we cannot know God exists, since that which transcends time simultaneously transcends human understanding.

Bradley saw reality as a monistic whole apprehended through "feeling", a state in which there is no distinction between the perception and the thing perceived. Like Berkeley Bradley thought that nothing can be known to exist unless it is known by a mind.

We perceive, on reflection, that to be real, or even barely to exist, must be to fall within sentience ... . Find any piece of existence, take up anything that any one could possibly call a fact, or could in any sense assert to have being, and then judge if it does not consist in sentient experience. Try to discover any sense in which you can still continue to speak of it, when all perception and feeling have been removed; or point out any fragment of its matter, any aspect of its being, which is not derived from and is not still relative to this source. When the experiment is made strictly, I can myself conceive of nothing else than the experienced.

— F.H. Bradley, 'Appearance and Reality', Chapter 14

Bradley was the apparent target of G. E. Moore's radical rejection of idealism. Moore claimed that Bradley did not understand the statement that something is real. We know for certain, through common sense and prephilosophical beliefs, that some things are real, whether they are objects of thought or not, according to Moore. The 1903 article The Refutation of Idealism is one of the first demonstrations of Moore's commitment to analysis. He examines each of the three terms in the Berkeleian aphorism esse est percipi, "to be is to be perceived", finding that it must mean that the object and the subject are necessarily connected so that "yellow" and "the sensation of yellow" are identical - "to be yellow" is "to be experienced as yellow". But it also seems there is a difference between "yellow" and "the sensation of yellow" and "that esse is held to be percipi, solely because what is experienced is held to be identical with the experience of it". Though far from a complete refutation, this was the first strong statement by analytic philosophy against its idealist predecessors, or at any rate against the type of idealism represented by Berkeley. This argument did not show that the GEM (in post–Stove vernacular, see below) is logically invalid.

Actual idealism[link]

Actual Idealism is a form of idealism developed by Giovanni Gentile that grew into a "grounded" idealism contrasting Kant and Hegel.

Pluralistic idealism[link]

Pluralistic idealism such as that of Gottfried Leibniz^[44] takes the view that there are many individual minds that together underlie the existence of the observed world and make possible the existence of the physical universe.^[45] Unlike absolute idealism, pluralistic idealism does not assume the existence of a single ultimate mental reality or "Absolute". Leibniz' form of idealism, known as Panpsychism, views "monads" as the true atoms of the universe and as entities having perception. The monads are "substantial forms of being",elemental, individual, subject to their own laws, non-interacting, each reflecting the entire universe. Monads are centers of force, which is substance while space, matter and motion are phenomenal and their form and existence is dependent on the simple and immaterial monads. There is a pre-established harmony established by God, the central monad, between the world in the minds of the monads and the external world of objects. Leibniz's cosmology embraced traditional Christian Theism. The English psychologist and philosopher James Ward inspired by Leibniz had also defended a form of pluralistic idealism.^[46] According to Ward the universe is composed of "psychic monads" of different levels, interacting for mutual self- betterment.^[47]

Personalism is the view that the minds that underlie reality are the minds of persons. Borden Parker Bowne, a philosopher at Boston University, a founder and popularizer of personal idealism, presented it as a substantive reality of persons, the only reality, as known directly in self-consciousness. Reality is a society of interacting persons dependent on the Supreme Person of God. Other proponents include George Holmes Howison^[48] and J. M. E. McTaggart.^[49]

Howison's personal idealism ^[50] was also called "California Personalism" by others to distinguish it from the "Boston Personalism" which was of Bowne. Howison maintained that both impersonal, monistic idealism and materialism run contrary to the experience of moral freedom. To deny freedom to pursue truth, beauty, and "benignant love" is to undermine every profound human venture, including science, morality, and philosophy. Personalistic idealists Borden Parker Bowne and Edgar S. Brightman and realistic personal theist Saint Thomas Aquinas address a core issue, namely that of dependence upon an infinite personal God.^[51]

Howison, in his book The Limits of Evolution and Other Essays Illustrating the Metaphysical Theory of Personal Idealism, created a democratic notion of personal idealism that extended all the way to God, who was no more the ultimate monarch but the ultimate democrat in eternal relation to other eternal persons. J. M. E. McTaggart's idealist atheism and Thomas Davidson's Apeirionism resemble Howisons personal idealism.^[52]

J. M. E. McTaggart of Cambridge University, argued that minds alone exist and only relate to each other through love. Space, time and material objects are unreal. In The Unreality of Time he argued that time is an illusion because it is impossible to produce a coherent account of a sequence of events. The Nature of Existence (1927) contained his arguments that space, time, and matter cannot possibly be real. In his Studies in Hegelian Cosmology (Cambridge, 1901, p196) he declared that metaphysics are not relevant to social and political action. McTaggart "thought that Hegel was wrong in supposing that metaphysics could show that the state is more than a means to the good of the individuals who compose it".^[53] For McTaggart "philosophy can give us very little, if any, guidance in action... Why should a Hegelian citizen be surprised that his belief as to the organic nature of the Absolute does not help him in deciding how to vote? Would a Hegelian engineer be reasonable in expecting that his belief that all matter is spirit should help him in planning a bridge?^[54]

Thomas Davidson taught a philosophy called "apeirotheism", a "form of pluralistic idealism...coupled with a stern ethical rigorism"^[55] which he defined as "a theory of Gods infinite in number." The theory was indebted to Aristotle's pluralism and his concepts of Soul, the rational, living aspect of a living substance which cannot exist apart from the body because it is not a substance but an essence, and nous, rational thought, reflection and understanding. Although a perennial source of controversy, Aristotle arguably views the latter as both eternal and immaterial in nature, as exemplified in his theology of unmoved movers.^[56] Identifying Aristotle's God with rational thought, Davidson argued, contrary to Aristotle, that just as the soul cannot exist apart from the body, God cannot exist apart from the world.^[57]

Idealism in the philosophy of science[link]

Nicolas Malebranche, though a student of Cartesian rationalism, disagreed that the existence of the external world is dubious and known only indirectly and declared instead that the real external world is actually God. For Malebranche we directly know internally the ideas in our mind. Externally, we directly know God's operations. This kind of idealism led to the pantheism of Spinoza.

Idealist notions took a strong hold among physicists of the early 20th century confronted with the paradoxes of quantum physics and the theory of relativity. In The Grammar of Science, Preface to the 2nd Edition, 1900, Karl Pearson wrote, "There are many signs that a sound idealism is surely replacing, as a basis for natural philosophy, the crude materialism of the older physicists." This book influenced Einstein's regard for the importance of the observer in scientific measurements^{[citation needed]}. In § 5 of that book, Pearson asserted that "...science is in reality a classification and analysis of the contents of the mind...." Also, "...the field of science is much more consciousness than an external world."

Sir Arthur Stanley Eddington, a British astrophysicist of the early 20th century, wrote in his book The Nature of the Physical World; "The stuff of the world is mind-stuff";

"The mind-stuff of the world is, of course, something more general than our individual conscious minds…. The mind-stuff is not spread in space and time; these are part of the cyclic scheme ultimately derived out of it…. It is necessary to keep reminding ourselves that all knowledge of our envi-ronment from which the world of physics is constructed, has entered in the form of messages transmitted along the nerves to the seat of consciousness…. Consciousness is not sharply defined, but fades into subconsciousness; and beyond that we must postulate something indefinite but yet continuous with our mental nature…. It is difficult for the matter-of-fact physicist to accept the view that the substratum of everything is of mental character. But no one can deny that mind is the first and most direct thing in our experience, and all else is remote inference."^[58]

Ian Barbour in his book Issues in Science and Religion (1966), p. 133, cites Arthur Eddington's The Nature of the Physical World (1928) for a text that argues The Heisenberg Uncertainty Principles provides a scientific basis for "the defense of the idea of human freedom" and his Science and the Unseen World (1929) for support of philosophical idealism "the thesis that reality is basically mental".

Sir James Jeans wrote; "The stream of knowledge is heading towards a non-mechanical reality; the Universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter... we ought rather hail it as the creator and governor of the realm of matter."^[59]

Jeans, in an interview published in The Observer (London), when asked the question:

Do you believe that life on this planet is the result of some sort of accident, or do you believe that it is a part of some great scheme?

replied:

I incline to the idealistic theory that consciousness is fundamental, and that the material universe is derivative from consciousness, not consciousness from the material universe... In general the universe seems to me to be nearer to a great thought than to a great machine. It may well be, it seems to me, that each individual consciousness ought to be compared to a brain-cell in a universal mind.

What remains is in any case very different from the full-blooded matter and the forbidding materialism of the Victorian scientist. His objective and material universe is proved to consist of little more than constructs of our own minds. To this extent, then, modem physics has moved in the direction of philosophic idealism. Mind and matter, if not proved to be of similar nature, are at least found to be ingredients of one single system. There is no longer room for the kind of dualism which has haunted philosophy since the days of Descartes. Sir James Jeans addressing the British Association in 1934.

Finite picture whose dimensions are a certain amount of space and a certain amount of time; the protons and electrons are the streaks of paint which define the picture against its space-time background. Traveling as far back in time as we can, brings us not to the creation of the picture, but to its edge; the creation of the picture lies as much outside the picture as the artist is outside his canvas. On this view, discussing the creation of the universe in terms of time and space is like trying to discover the artist and the action of painting, by going to the edge of the canvas. This brings us very near to those philosophical systems which regard the universe as a thought in the mind of its Creator, thereby reducing all discussion of material creation to futility. Sir James Jeans The Universe Around Us page 317.

The chemist Ernest Lester Smith wrote a book Intelligence Came First (1975) in which he claimed that consciousness is a fact of nature and that the cosmos is grounded in and pervaded by mind and intelligence.^[60]

Bernard d'Espagnat a French theoretical physicist best known for his work on the nature of reality wrote a paper titled The Quantum Theory and Reality according to the paper: "The doctrine that the world is made up of objects whose existence is independent of human consciousness turns out to be in conflict with quantum mechanics and with facts established by experiment."^[61] In an article in the Guardian titled Quantum weirdness: What we call 'reality' is just a state of mind d'Espagnat wrote that:

"What quantum mechanics tells us, I believe, is surprising to say the least. It tells us that the basic components of objects – the particles, electrons, quarks etc. – cannot be thought of as "self-existent". He further writes that his research in quantum physics has lead him to conclude that an "ultimate reality" exists, which is not embedded in space or time.^[62]

Notes[link]

References[link]

• Immanuel Kant's Critique of Pure Reason with an historical introduction by Ludwig Noiré, available at [4]
• Kierkegaard, Søren. Concluding Unscientific Postscript, Princeton, ISBN 978-0-691-02081-5
• Neujahr, Philip J., Kant's Idealism, Mercer University Press, 1995 ISBN 0-86554-476-X
• Watts, Michael. Kierkegaard, Oneworld, ISBN 978-1-85168-317-8

Further reading

• Gustavus Watts Cunningham Idealistic Argument in Recent British and American Philosophy Books For Libraries Press, 1967
• Hugh Joseph Tallon The concept of self in British and American idealism Catholic University of America Press, 1939
• Gerald Thomas Baskfield The idea of God in British and American personal idealism Catholic University of America, 1933
• Vergilius Ture Anselm Ferm A history of philosophical systems Littlefield Adams, 1968 ISBN 0-8226-0130-3

External links[link]

Look up idealism in Wiktionary, the free dictionary.

• A.C. Grayling-Wittgenstein on Scepticism and Certainty
• Science and Health with Key to the Scriptures by Mary Baker Eddy: idealism in religious thought
• Idealism and its practical use in physics and psychology
• 'The Triumph of Idealism', lecture by Professor Keith Ward offering a positive view of Idealism, at Gresham College, 13 March 2008 (available in text, audio, and video download)

Keith Ward (born 22 August 1938) is a British cleric, philosopher, theologian and scholar. He is a Fellow of the British Academy and (since 1972) an ordained priest of the Church of England. He was a canon of Christ Church, Oxford until 2003. Comparative theology and the interplay between science and faith are two of his main topics of interest.

Academic work[link]

Ward graduated in 1962 with a BA from the University of Wales, and from 1964-69 was a Lecturer in Logic at the University of Glasgow. He earned a BLitt from Linacre College, Oxford in 1968. From 1969-1971 he was Lecturer in Philosophy at the University of St Andrews. In 1972, he was ordained priest in the Church of England. From 1971-75 he was Lecturer in Philosophy of Religion at the University of London. From 1975-83, he was Dean of Trinity Hall, Cambridge. He was appointed F. D. Maurice Professor of Moral and Social Theology at the University of London in 1982, Professor of History and Philosophy of Religion at King's College London in 1985, and Regius Professor of Divinity at Oxford in 1991, a post from which he retired in 2004.^[1]

In 1992, he was a visiting professor at the Claremont Graduate University in California. In 1993-94, he delivered the prestigious Gifford Lectures at the University of Glasgow. Ward was the Gresham Professor of Divinity between 2004 and 2008 at Gresham College, London.^[2]

He is on the council of the Royal Institute of Philosophy and is a member of the Editorial Boards of Religious Studies, Journal of Contemporary Religion, Studies in Inter-Religious Dialogue and World Faiths Encounter. He is a member of the Board of Governors of the Oxford Centre for Hindu Studies. He has also been a visiting professor at Drake University, Iowa, and at the University of Tulsa, Oklahoma.^[3]

Ward has an MA and DD degrees from both Cambridge and Oxford,^[4] and an honorary DD from the University of Glasgow.

Focus and beliefs[link]

One of his main focuses is the dialogue between religious traditions, an interest which led him to be Joint President of the World Congress of Faiths (WCF) between 1992 and 2001. His work also explores concepts of God and the idea of revelation. Ward has also written about his opinion of a relationship between science and religion.^[5] As an advocate of theistic evolution, he regards them as essentially compatible, a belief he has described in his book God, Chance and Necessity, and which is in contrast to his Oxford colleague Richard Dawkins, an ethologist and vocal and prominent atheist. Ward has said that Dawkins's conclusion that there is no God or any purpose in the universe is "naive" and not based on science but on a hatred of religion. Dawkins's strong anti-religious views originate, according to Ward, from earlier encounters with "certain forms of religion which are anti-intellectual and anti-scientific...and also emotionally pressuring."^[6] He has also been highly critical of materialist philosophers of consciousness such as Daniel Dennett, as well as social scientists such as Sigmund Freud and Karl Marx, arguing that they each attempt to reduce the human person into aspects of their own discipline. Ward has described his own Christian faith as follows:

I am a born-again Christian. I can give a precise day when Christ came to me and began to transform my life with his power and love. He did not make me a saint. But he did make me a forgiven sinner, liberated and renewed, touched by divine power and given the immense gift of an intimate sense of the personal presence of God. I have no difficulty in saying that I wholeheartedly accept Jesus as my personal Lord and Saviour.^[7]

He has criticized modern day Christian fundamentalism, most notably in his 2004 book What the Bible Really Teaches: A Challenge for Fundamentalists. He believes that fundamentalists interpret the Bible in implausible ways and pick and choose which of its passages to emphasise in order to fit pre-existing beliefs. Ward argues that the Bible must be taken seriously, but not always literally and he does not agree with the doctrine of Biblical inerrancy, saying that it is not found in the Bible, elaborating that

There may be discrepancies and errors in the sacred writings, but those truths that God wished to see included in the Scripture, and which are important to our salvation, are placed there without error... the Bible is not inerrant in detail, but God has ensured that no substantial errors, which mislead us about the nature of salvation, are to be found in Scripture.^[7]

Books[link]

Ward is the author of over 20 books including:

• Ethics and Christianity (1970) ISBN 978-0-04-241001-2
• Divine Image (1976) ISBN 978-0-281-02935-8
• Christian Way (1976) ISBN 978-0-281-02893-1
• The Concept of God (1977) ISBN 978-0-312-15925-2
• Rational Theology and the Creativity of God (1982)
• Holding Fast to God (1982) ISBN 978-0-687-85476-9 – a critique of Taking Leave of God by the radical theologian Don Cupitt
• Living God (1984) ISBN 978-0-281-04126-8
• The Battle for the Soul (1985) ISBN 978-0-340-37278-4
• Images of Eternity (1987) ISBN 978-0-232-51686-9
• The Rule of Love (1989) ISBN 978-0-232-51824-5
• A Vision to Pursue (1991) ISBN 978-0-334-02411-8
• Is Christianity a Historical Religion? (1992) ISBN 978-0-85217-054-0
• Religion and Revelation (1994) ISBN 978-0-19-826375-3 (1993-94 Gifford Lectures, [1])
• Religion and Creation (1996) ISBN 978-0-19-826394-4
• God, Chance and Necessity (1996) ISBN 978-1-85168-116-7
• Concepts of God (1998) ISBN 978-1-85168-064-1
• Religion and Human Nature (1998) ISBN 978-0-19-826965-6
• God, Faith and the New Millennium (1998)
• In Defence of the Soul (1998) ISBN 978-1-85168-040-5
• Christianity: A Short Introduction (2000) ISBN 978-1-85168-229-4
• Religion and Community (2000) ISBN 978-0-19-875259-2
• God, A Guide for the Perplexed (2002) ISBN 978-1-85168-323-9
• What the Bible Really Teaches: A Challenge for Fundamentalists (2004) ISBN 978-0-281-05680-4
• Pascal's Fire - Scientific Faith and Religious Understanding (2006) ISBN 978-1-85168-446-5
• Is Religion Dangerous? (2006) ISBN 978-0-7459-5262-8
• Re-thinking Christianity (2007) ISBN 978-1-85168-506-6
• The Big Questions in Science and Religion (2008)
• Why There Almost Certainly Is a God (2008) ISBN 978-0-7459-5330-4 (UK) ISBN 978-0-8254-7843-7 (US)
• Divine Action: Examining God's Role in an Open and Emergent Universe (2008)
• Religion & Human Fulfilment (2008) ISBN 978-0-334-04163-4
• The God Conclusion (2009)
• More Than Matter: What Humans Really Are (2010) ISBN 978-0-7459-6247-4

Books about Keith Ward and his theology include:

• Comparative Theology: Essays for Keith Ward ed T W Bartel (2003) ISBN 978-0-281-05474-9

Multimedia[link]

• Keith Ward (13 March 2008). The Triumph of Idealism. London: Gresham College. http://www.gresham.ac.uk/lectures-and-events/the-triumph-of-idealism.  (58:00). Downloadable video, audio & transcript. Five other lectures by Keith Ward, recorded 2007-09 are available.
• Video interview by Robert Wright (39:35).
• Philosophy, Science and The God Debate, a two-DVD set of filmed interviews with Keith Ward, Alister McGrath and John Lennox, and produced by the Nationwide Christian Trust, ISBN 5055307601776 (November 2011)^[8]

See also[link]

• Boyle Lectures

External links[link]

• KeithWard.org.uk
• Article criticizing Richard Dawkins' TV series 'The Root of all Evil?'
• Keith Ward, Metanexus Senior Fellow

References[link]

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2010)

George Berkeley

Born	(1685-03-12)12 March 1685 County Kilkenny, Ireland
Died	14 January 1753(1753-01-14) (aged 67) Oxford, England
Era	18th century philosophy
Region	Western Philosophy
School	Idealism, Empiricism
Main interests	Christianity, Metaphysics, Epistemology, Language, Mathematics, Perception
Notable ideas	Subjective idealism, master argument
Influenced by John Locke, Isaac Newton, Nicolas Malebranche
Influenced David Hume, Edmund Burke, Immanuel Kant, Thomas Reid, Arthur Schopenhauer, John Stuart Mill, Ernst Mach, A.J. Ayer, Jorge Luis Borges, Samuel Beckett

George Berkeley ( /ˈbɑrkliː/;^[1] 12 March 1685 – 14 January 1753), also known as Bishop Berkeley (Bishop of Cloyne), was an Anglo-Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism" (later referred to as "subjective idealism" by others). This theory denies the existence of material substance and instead contends that familiar objects like tables and chairs are only ideas in the minds of perceivers, and as a result cannot exist without being perceived. Thus, as Berkeley famously put it, for physical objects "esse est percipi" ("to be is to be perceived"). Berkeley is also known for his critique of abstraction, an important premise in his argument for immaterialism.

In 1709, Berkeley published his first major work, An Essay towards a New Theory of Vision, in which he discussed the limitations of human vision and advanced the theory that the proper objects of sight are not material objects, but light and color. This foreshadowed his chief philosophical work A Treatise Concerning the Principles of Human Knowledge in 1710 which, after its poor reception, he rewrote in dialogue form and published under the title Three Dialogues between Hylas and Philonous in 1713.^[2]
In this book, Berkeley's views were represented by Philonous (Greek: 'lover of mind'), while Hylas (Greek: 'matter') embodies the Irish thinker’s opponents, in particular John Locke. Berkeley argued against Sir Isaac Newton's doctrine of absolute space, time and motion in De Motu^[3] (on Motion), published 1721. His arguments were a precursor to the views of Mach and Einstein.^[4] In 1732, he published Alciphron, a Christian apologetic against the free-thinkers, and in 1734, he published The Analyst, an empiricist critique of the foundations of infinitesimal calculus, which was influential in the development of mathematics.

His last major philosophical work, Siris (1744), begins by advocating the medicinal use of tar water, and then continues to discuss a wide range of topics including science, philosophy, and theology. Interest in Berkeley's work increased after World War II, because he tackled many of the issues of paramount interest to philosophy in the 20th century such as the problems of perception, the difference between primary and secondary qualities, and the importance of language.^[5]

Life[link]

Berkeley was born at his family home, Dysart Castle, near Thomastown, County Kilkenny, Ireland, the eldest son of William Berkeley, a cadet of the English noble family of Berkeley. He was educated at Kilkenny College and attended Trinity College, Dublin, completing a Master's degree in 1707. He remained at Trinity College after completion of his degree as a tutor and Greek lecturer.

His earliest publication was on mathematics, but the first that brought him notice was his Essay Towards a New Theory of Vision, first published in 1709. In the essay, Berkeley examines visual distance, magnitude, position and problems of sight and touch. While this work raised much controversy at the time, its conclusions are now accepted as an established part of the theory of optics.

The next publication to appear was the Treatise Concerning the Principles of Human Knowledge in 1710 which had great success and gave him a lasting reputation, though few accepted his theory that nothing exists outside the mind. This was followed in 1713 by Three Dialogues between Hylas and Philonous, in which he propounded his system of philosophy, the leading principle of which is that the world, as represented by our senses, depends for its existence on being perceived.

For this theory, the Principles gives the exposition and the Dialogues the defence. One of his main objectives was to combat the prevailing materialism of his time. The theory was largely received with ridicule; while even those, such as Samuel Clarke and William Whiston, who did acknowledge his "extraordinary genius," were nevertheless convinced that his first principles were false.

England and Europe[link]

Shortly afterwards, Berkeley visited England, and was received into the circle of Addison, Pope and Steele. In the period between 1714 and 1720, he interspersed his academic endeavors with periods of extensive travel in Europe, including one of the most extensive Grand Tours of the length and breadth of Italy ever undertaken.^[6] In 1721, he took Holy Orders in the Church of Ireland, earning his doctorate in divinity, and once again chose to remain at Trinity College Dublin, lecturing this time in Divinity and in Hebrew. In 1724, he was made Dean of Derry.

In 1725, he began the project of founding a college in Bermuda for training ministers and missionaries in the colony, in pursuit of which he gave up his deanery with its income of £1100.

Marriage and America[link]

In 1728, he married Anne Forster, daughter of the Lord Chief Justice of Ireland. He then went to America on a salary of £100 per annum. He landed near Newport, Rhode Island, where he bought a plantation in Middletown, Rhode Island – the famous "Whitehall". He lived at the plantation while he waited for funds for his college to arrive. The funds, however, were not forthcoming and, in 1732, he left America and returned to London.

Humanitarian work[link]

While living in London's Saville Street, he took part in efforts to create a home for the city's abandoned children. The Foundling Hospital was founded by Royal Charter in 1739 and Berkeley is listed as one of its original governors. In 1734, he was appointed Bishop of Cloyne in Ireland, a position he was to hold until his death. Soon afterwards, he published Alciphron, or The Minute Philosopher, directed against both Shaftesbury and Bernard de Mandeville; and in 1735–37 The Querist.

Last works[link]

His last two publications were Siris: Philosophical reflexions and inquiries concerning the virtues of tar-water, and divers other subjects connected together and arising from one another (1744) and Further Thoughts on Tar-water (1752). Pine tar is an effective antiseptic and disinfectant when applied to cuts on the skin, but Berkeley argued for the use of pine tar as a broad panacea for diseases. It is said that his 1744 book on the medical benefits of pine tar was the best-selling book in his lifetime.^[7]

He remained at Cloyne until 1752, when he retired and went to Oxford to live with his son. He died soon afterward and was buried in Christ Church Cathedral, Oxford. His affectionate disposition and genial manners made him much loved and held in warm regard by many of his contemporaries.^{[citation needed]}

Contributions to philosophy[link]

According to Berkeley there are only two kinds of things: spirits and ideas. Spirits are simple, active beings which produce and perceive ideas; ideas are passive beings which are produced and perceived.^[8]

The use of the concepts of “spirit” and “idea” is central in Berkeley’s philosophy. As used by him, these concepts are difficult to translate into modern terminology. His concept of “spirit” is close to the concept of “conscious subject” or of “mind”, and the concept of “idea” is close to the concept of “sensation” or “state of mind” or “conscious experience”.

Thus Berkeley denied the existence of matter as a metaphysical substance, but did not deny the existence of physical objects such as apples or mountains. ("I do not argue against the existence of any one thing that we can apprehend, either by sense or reflection. That the things I see with mine eyes and touch with my hands do exist, really exist, I make not the least question. The only thing whose existence we deny, is that which philosophers call matter or corporeal substance. And in doing of this, there is no damage done to the rest of mankind, who, I dare say, will never miss it.", Principles #35) This basic claim of Berkeley's thought is called "immaterialism" or, more commonly, subjective idealism. Incidentally, this claim is fundamentally different from the claim, sometimes inaccurately attributed to Berkeley, that to be is to be perceived (esse est percipi).^[9]

Hence, human knowledge is reduced to two elements: that of spirits and of ideas (Principles #86). In contrast to ideas, a spirit cannot be perceived. A person's spirit, which perceives ideas, is to be comprehended intuitively by inward feeling or reflection (Principles #89). For Berkeley, we have no direct 'idea' of spirits, albeit we have good reason to believe in the existence of other spirits, for their existence explains the purposeful regularities we find in experience.^[10] (“It is plain that we cannot know the existence of other spirits otherwise than by their operations, or the ideas by them excited in us”, Dialogues #145). This is the solution that Berkeley offers to the problem of other minds. Finally, the order and purposefulness of the whole of our experience of the world and especially of nature overwhelms us into believing in the existence of an extremely powerful and intelligent spirit that causes that order. According to Berkeley, reflection on the attributes of that external spirit leads us to identify it with God. Thus a material thing such as an apple consists of a collection of ideas (shape, color, taste, physical properties, etc.) which are caused in the spirits of humans by the spirit of God.

Theology[link]

A convinced adherent of Christianity, Berkeley believed God to be present as an immediate cause of all our experiences.

He did not evade the question of the external source of the diversity of the sense data at the disposal of the human individual. He strove simply to show that the causes of sensations could not be things, because what we called things, and considered without grounds to be something different from our sensations, were built up wholly from sensations. There must consequently be some other external source of the inexhaustible diversity of sensations. The source of our sensations, Berkeley concluded, could only be God; He gave them to man, who had to see in them signs and symbols that carried God’s word.^[11]

Here is Berkeley's proof of the existence of God:

Whatever power I may have over my own thoughts, I find the ideas actually perceived by Sense have not a like dependence on my will. When in broad daylight I open my eyes, it is not in my power to choose whether I shall see or no, or to determine what particular objects shall present themselves to my view; and so likewise as to the hearing and other senses; the ideas imprinted on them are not creatures of my will. There is therefore some other Will or Spirit that produces them. (Berkeley. Principles #29)

As T.I. Oizerman explained:

Berkeley’s mystic idealism (as Kant aptly christened it) claimed that nothing separated man and God (except materialist misconceptions, of course), since nature or matter did not exist as a reality independent of consciousness. The revelation of God was directly accessible to man, according to this doctrine; it was the sense-perceived world, the world of man's sensations, which came to him from on high for him to decipher and so grasp the divine purpose.^[11]

Berkeley believed that God is not the distant engineer of Newtonian machinery that in the fullness of time led to the growth of a tree in the university quadrangle. Rather, the perception of the tree is an idea that God's mind has produced in the mind, and the tree continues to exist in the quadrangle when "nobody" is there, simply because God is an infinite mind that perceives all.

The philosophy of David Hume concerning causality and objectivity is an elaboration of another aspect of Berkeley's philosophy. A.A. Luce, the most eminent Berkeley scholar of the 20th century, constantly stressed the continuity of Berkeley's philosophy. The fact that Berkeley returned to his major works throughout his life, issuing revised editions with only minor changes, also counts against any theory that attributes to him a significant volte-face.^{[citation needed]}

Relativity arguments[link]

John Locke (Berkeley's predecessor) states that we define an object by its primary and secondary qualities. He takes heat as an example of a secondary quality. If you put one hand in a bucket of cold water, and the other hand in a bucket of warm water, then put both hands in a bucket of lukewarm water, one of your hands is going to tell you that the water is cold and the other that the water is hot. Locke says that since two different objects (both your hands) perceive the water to be hot and cold, then the heat is not a quality of the water.

While Locke used this argument to distinguish primary from secondary qualities, Berkeley extends it to cover primary qualities in the same way. For example, he says that size is not a quality of an object because the size of the object depends on the distance between the observer and the object, or the size of the observer. Since an object is a different size to different observers, then size is not a quality of the object. Berkeley rejects shape with a similar argument and then asks: if neither primary qualities nor secondary qualities are of the object, then how can we say that there is anything more than the qualities we observe?

New theory of vision[link]

This section requires expansion.

In his Essay Towards a New Theory of Vision, Berkeley frequently criticised the views of the Optic Writers, a title that seems to include Molyneux, Wallis, Malebranche and Descartes.^[12] In sections 1-51, Berkeley argued against the classical scholars of optics by holding that: spatial depth, as the distance that separates the perceiver from the perceived object is itself invisible; namely, that space is perceived by experience instead of the senses per se.

Berkeley goes on to argue that visual cues, such as the perceived extension or 'confusion' of an object, can only be used to indirectly judge distance, because the viewer learns to associate visual cues with tactile sensations. Berkeley gives the following analogy regarding indirect distance perception: one perceives distance indirectly just as one perceives a person's embarrassment indirectly. When looking at an embarrassed person, we infer indirectly that the person is embarrassed by observing the red color on the person's face. We know through experience that a red face tends to signal embarrassment, as we've learned to associate the two.

The question concerning the visibility of space was central to the Renaissance perspective tradition and its reliance on classical optics in the development of pictorial representations of spatial depth. This matter was debated by scholars since the 11th century Arab polymath and mathematician Alhazen (al-Hasan Ibn al-Haytham) affirmed in experimental contexts the visibility of space. This issue, which was raised in Berkeley's theory of vision, was treated at length in the Phenomenology of Perception of Maurice Merleau-Ponty, in the context of confirming the visual perception of spatial depth (la profondeur), and by way of refuting Berkeley's thesis.^[13]

Berkeley wrote about the perception of size in addition to that of distance. He is frequently misquoted as believing in size-distance invariance — a view held by the Optic Writers. This idea is that we scale the image size according to distance in a geometrical manner. The error may have become commonplace, because the eminent historian and psychologist E.G. Boring perpetuated it.^[14] In fact Berkeley argued that the same cues that evoke distance also evoke size, and that we do not first see size and then calculate distance.^[15] It is worth quoting Berkeley’s words on this issue (Section 53):

“What inclines men to this mistake (beside the humour of making one see by geometry) is, that the same perceptions or ideas which suggest distance, do also suggest magnitude… I say they do not first suggest distance, and then leave it to the judgement to use that as a medium, whereby to collect the magnitude; but they have as close and immediate a connexion with the magnitude as with the distance; and suggest magnitude as independently of distance, as they do distance independently of magnitude.”

Philosophy of physics[link]

This section requires expansion.

"Berkeley’s works display his keen interest in natural philosophy [...] from his earliest writings (Arithmetica, 1707) to his latest (Siris, 1744). Moreover, much of his philosophy is shaped fundamentally by his engagement with the science of his time."^[16] How profound this interest was can be judged from numerous entries in Berkeley’s Philosophical Commentaries (1707–1708), e.g. "Mem. to Examine & accurately discuss the scholium of the 8th Definition of Mr Newton’s Principia." (#316)

Philosophy of mathematics[link]

In addition to his contributions to philosophy, Bishop Berkeley was also very influential in the development of mathematics, although in a rather indirect sense. "Berkeley was concerned with mathematics and its philosophical interpretation from the earliest stages of his intellectual life."^[17] Berkeley’s “Philosophical Commentaries” (1707–1708) witness to his interest in mathematics:

Axiom. No reasoning about things whereof we have no idea. Therefore no reasoning about Infinitesimals. (#354) Take away the signs from Arithmetic & Algebra, & pray what remains? (#767) These are sciences purely Verbal, & entirely useless but for Practise in Societys of Men. No speculative knowledge, no comparison of Ideas in them. (#768)

In 1707, Berkeley published two treatises on mathematics. In 1734, he published The Analyst, subtitled A DISCOURSE Addressed to an Infidel Mathematician, a critique of the Calculus. Florian Cajori called this treatise “the most spectacular event of the century in the history of British mathematics.”^[18] However, a recent study suggests that Berkeley misunderstood Leibnizian calculus.^[19] The mathematician in question is believed to have been either Edmond Halley, or Isaac Newton himself—though if to the latter, then the discourse was posthumously addressed, as Newton died in 1727. The Analyst represented a direct attack on the foundations and principles of Infinitesimal calculus and, in particular, the notion of fluxion or infinitesimal change, which Newton and Leibniz used to develop the calculus. Berkeley coined the phrase Ghosts of departed quantities, familiar to students of calculus. Ian Stewart's book From Here to Infinity, (chapter 6), captures the gist of his criticism.

Berkeley regarded his criticism of calculus as part of his broader campaign against the religious implications of Newtonian mechanics – as a defense of traditional Christianity against deism, which tends to distance God from His worshipers.

The difficulties raised by Berkeley were still present in the work of Cauchy whose approach to infinitesimal calculus was a combination of infinitesimals and a notion of limit, and were eventually sidestepped by Weierstrass by means of his (ε, δ) approach, which eliminated infinitesimals altogether. More recently, Abraham Robinson restored infinitesimal methods in his 1966 book Non-standard analysis by showing that they can be used rigorously.

Moral philosophy[link]