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The unmoved mover (οὐ κινούμενον κινεῖ ou kinoúmenon kineῖ) is a philosophical concept described by Aristotle as a primary cause or "mover" of all the motion in the universe.^[1] As is implicit in the name, the "unmoved mover" is not moved by any prior action. In Book 12 (Greek "Λ") of his Metaphysics, Aristotle describes the unmoved mover as being perfectly beautiful, indivisible, and contemplating only the perfect contemplation: itself contemplating. He equates this concept also with the Active Intellect. This Aristotelian concept had its roots in cosmological speculations of the earliest Greek "Pre-Socratic" philosophers and became highly influential and widely drawn upon in medieval philosophy and theology. St. Thomas Aquinas, for example, elaborated on the Unmoved Mover in the quinque viae.

First philosophy[link]

Aristotle argues, in Book 8 of the Physics Book 12 of the Metaphysics "that there must be an immortal, unchanging being, ultimately responsible for all wholeness and orderliness in the sensible world. And he is able … to discover a good deal about that being”.^[2] In the Physics (VIII 4–6) Aristotle finds "surprising difficulties" explaining even commonplace change, and in support of his approach of explanation by four causes, he required "a fair bit of technical machinery".^[3] This "machinery" includes potentiality and actuality, hylomorphism, category theory, and “an audacious and intriguing argument, that the bare existence of change requires the postulation of a first cause, an unmoved mover whose necessary existence underpins the ceaseless activity of the world of motion”.^[4] Aristotle's "first philosophy", or Metaphysics (“after the Physics”), develops his peculiar stellar theology of the prime mover, as πρῶτον κινοῦν ἀκίνητον: an independent divine eternal unchanging immaterial substance.^[5]

Celestial spheres[link]

Aristotle adopted the geometrical model of Eudoxus of Cnidus, to provide a general explanation of the apparent wandering of the classical planets arising from uniform circular motions of celestial spheres.^[6] While the number of spheres in the model itself was subject to change, (47 or 55), Aristotle's account of aether, and of potentiality and actuality, required an individual unmoved mover for each sphere.^[7]

Final cause and efficient cause[link]

Despite their apparent function in the celestial model, the unmoved movers were a final cause, not an efficient cause for the movement of the spheres; they were solely a constant inspirational,^[8] and even if taken for an efficient cause precisely due to being a final cause,^[9] the nature of the explanation is purely teleological.^[10]

“These issues are sharpened by the objection that in the natural cases at least teleological and material-efficient explanations are actually incompatible. The objection goes as follows. Suppose some explanandum E, and a set of conditions C which account for E mechanistically. It is then reasonable to suppose that the instantiation of C necessitates E. Now take some supposed final cause F: if it is going to be even part of the explanation of E, it should be at least a necessary condition of E. But the only way for that to be true compatibly with C's necessitating E is if F is at least necessary for C as well. But how can final causes be necessary for the material instantiation of the mechanistic causes of things?
Material-efficient and non-intentional teleological explanations of naturally occurring events are incompatible. If the teleology is of the consciously directed kind, there is no problem: it is easy to see how the conception of the goal figures in the causal story which gets the means to that sufficiently strongly to allow some genuine explanatory power without courting the incoherence raised above…”

— R. J. Hankinson, Cause and Explanation in Ancient Greek Thought, pp.116–117

Aristotle's theology[link]

The unmoved movers, if they were anywhere, were said to fill the outer void, beyond the sphere of fixed stars:

“It is clear then that there is neither place, nor void, nor time, outside the heaven. Hence whatever is there, is of such a nature as not to occupy any place, nor does time age it; nor is there any change in any of the things which lie beyond the outermost motion; they continue through their entire duration unalterable and unmodified, living the best and most self sufficient of lives… From [the fulfilment of the whole heaven] derive the being and life which other things, some more or less articulately but other feebly, enjoy.”^[11]

— Aristotle, De Caelo, I.9, 279 a17–30

The unmoved movers are, themselves, immaterial substance, (separate and individual beings), having neither parts nor magnitude. As such, it would be physically impossible for them to move material objects of any size by pushing, pulling or collision. Because matter is, for Aristotle, a substratum in which a potential to change can be actualized, any and all potentiality must be actualized in a being that is eternal but it must not be still, because continuous activity is essential for all forms of life. This immaterial form of activity must be intellectual in nature and it cannot be contingent upon sensory perception if it is to remain uniform; therefore eternal substance must think only of thinking itself and exist outside the starry sphere, where even the notion of place is undefined for Aristotle. Their influence on lesser beings is purely the result of an "aspiration or desire"^[12], and each aetheric celestial sphere emulates one of the unmoved movers, as best it can, by uniform circular motion. The first heaven, the outmost sphere of fixed stars, is moved by a desire to emulate the prime mover (first cause),^[13][14] in relation to whom, the subordinate movers suffer an accidental dependency.

Many of Aristotle's contemporaries complained that oblivious, powerless gods are unsatisfactory.^[5] Nonetheless, it was a life which Aristotle enthusiastically endorsed as one most enviable and perfect, the unembellished basis of theology. As the whole of nature depends on the inspiration of the eternal unmoved movers, Aristotle was concerned to establish the metaphysical necessity of the perpetual motions of the heavens. It is through the seasonal action of the Sun upon the terrestrial spheres, that the cycles of generation and corruption give rise to all natural motion as efficient cause.^[10] The intellect, nous, "or whatever else it be that is thought to rule and lead us by nature, and to have cognizance of what is noble and divine" is the highest activity, according to Aristotle (contemplation or speculative thinking, theōrētikē). It is also the most sustainable, pleasant, self-sufficient activity;^[15] something which is aimed at for its own sake. (In contrast to politics and warfare, it does not involve doing things we'd rather not do, but rather something we do at our leisure.) This aim is not strictly human, to achieve it means to live in accordance not with mortal thoughts, but something immortal and divine which is within humans. According to Aristotle, contemplation is the only type of happy activity which it would not be ridiculous to imagine the gods having. In Aristotle's psychology and biology, the intellect is the soul, (see also eudaimonia).

First cause[link]

In book VIII of his Physics,^[16] Aristotle examines the notions of change or motion, and attempts to show by a challenging argument, that the mere supposition of a ‘before’ and an ‘after’, requires a first principle. He argues that in the beginning, if the cosmos had come to be, its first motion would lack an antecedent state, and as Parmenides said, "nothing comes from nothing". The Cosmological argument, later attributed to Aristotle, thereby draws the conclusion that God exists. However, in Aristotle's estimation, he has proved there can be motion without eternal motion, and thus the cosmos has neither a beginning nor an end.^[7]

“But it is a wrong assumption to suppose universally that we have an adequate first principle in virtue of the fact that something always is so … Thus Democritus reduces the causes that explain nature to the fact that things happened in the past in the same way as they happen now: but he does not think fit to seek for a first principle to explain this ‘always’ … Let this conclude what we have to say in support of our contention that there never was a time when there was not motion, and never will be a time when there will not be motion.” (Physics VIII, 2)^[17]

The purpose of Aristotle's cosmological argument, that at least one eternal unmoved mover must exist, is to support everyday change.^[18]

“Of things that exist, substances are the first. But if substances can, then all things can perish... and yet, time and change cannot. Now, the only continuous change is that of place, and the only continuous change of place is circular motion. Therefore, there must be an eternal circular motion and this confirmed by the fixed stars which are moved by the eternal actual substance substance that's purely actual.”^[19]

If the cosmos had a beginning, Aristotle argued, it would require an efficient first cause, a notion that Aristotle took to demonstrate a critical flaw.

Substance and change[link]

Aristotle begins by describing substance, of which he says there are three types: the sensible, which is subdivided into the perishable, which belongs to physics, and the eternal, which belongs to “another science.” He notes that sensible substance is changeable and that there are several types of change, including quality and quantity, generation and destruction, increase and diminution, alteration, and motion. Change occurs when one given state becomes something contrary to it: that is to say, what exists potentially comes to exist actually. (See Potentiality and actuality.) Therefore, “a thing [can come to be], incidentally, out of that which is not, [and] also all things come to be out of that which is, but is potentially, and is not actually.” That by which something is changed is the mover, that which is changed is the matter, and that into which it is changed is the form.

Substance is necessarily composed of different elements. The proof for this is that there are things which are different from each other and that all things are composed of elements. Since elements combine to form composite substances, and because these substances differ from each other, there must be different elements: in other words, “b or a cannot be the same as ba.”

The number of movers[link]

Near the end of Metaphysics, Book Λ, Aristotle introduces a surprising question, asking "whether we have to suppose one such [mover] or more than one, and if the latter, how many."^[20] Aristotle concludes that the number of all the movers equals the number of separate movements, and we can determine these by considering the mathematical science most akin to philosophy, i.e., astronomy. Although the mathematicians differ on the number of movements, Aristotle considers that the number of spheres would be 47 or 55. Nonetheless, he concludes his Metaphysics, Book Λ, with a quotation from the Iliad: “The rule of many is not good; one ruler let there be.”^[21][22]

See also[link]

• Primum Mobile
• Primum movens
• The All
• Causeless cause
• Chaos (cosmogony)
• Cosmological argument
• Dynamics of the celestial spheres
• Godhead
• Logos
• The One; Monad

Notes[link]