- published: 03 May 2014
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The English word theory was derived from a technical term in philosophy in Ancient Greek. The word theoria, θεωρία, meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action. Theory is especially often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for "doing", which is opposed to theory because theory involved no doing apart from itself.
A classical example of the distinction between theoretical and practical uses the discipline of medicine: Medical theory and theorizing involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.
By extension of the philosophical meaning, "theoria" is also a word still used in theological contexts.
Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future. Time is a component quantity of many measurements used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. The temporal position of events with respect to the transitory present is continually changing; events happen, then are located further and further in the past. Time has been a major subject of religion, philosophy, and science, but defining it in a manner applicable to all fields of study without circularity has consistently eluded scholars. A simple definition states that "time is what clocks measure".
Time is one of the seven fundamental physical quantities in the International System of Units. Time is used to define other quantities — such as velocity — so defining time in terms of such quantities would result in circularity of definition. An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, is highly useful in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called spacetime bring questions about space into questions about time, questions that have their roots in the works of early students of natural philosophy.
William Lane Craig (born August 23, 1949) is an American analytic philosopher, philosophical theologian, and Christian apologist. He is known for his work in the philosophy of religion, philosophy of time, and the defense of Christian theism. One of his most notable contributions to the philosophy of religion is his defense of the Kalām cosmological argument, which is the most widely discussed argument for the existence of God in contemporary Western philosophy. In theology, he has also defended Molinism and the belief that God is, since Creation, subject to time.
Craig has authored or edited over 30 books, including The Kalām Cosmological Argument (1979), The Cosmological Argument from Plato to Leibniz (1980), Theism, Atheism, and Big Bang Cosmology (with Quentin Smith, 1993), Philosophical Foundations for a Christian Worldview (with J.P. Moreland, 2003) and Reasonable Faith: Christian Truth and Apologetics (3d edition, 2008).
Craig received a Bachelor of Arts degree in communications from Wheaton College, Illinois, in 1971 and two summa cum laude master's degrees from Trinity Evangelical Divinity School in Deerfield, Illinois, in 1975, in philosophy of religion and ecclesiastical history. He earned a Ph.D. in philosophy under John Hick at the University of Birmingham, England in 1977 and a Th.D. under Wolfhart Pannenberg at the University of Munich in 1984.