The causal argument
The argument for the existence of God inferred from motion was given a more familiar form in the first of the five ways of St. Thomas
Aquinas, five major proofs of God that also owed much to the emphasis on the complete transcendence of God in the teaching of
Plotinus, the leading Neoplatonist of the 3rd century AD, and his followers. (The word that Plotinus used for the ultimate but mysterious dependence of all things on God is emanation; but this characterization was not understood by him, as it has been by some later thinkers, as questioning the genuine independent existence of finite things.) In the first way, Aquinas put forward the view that all movement implies, in the last analysis, an unmoved mover; and though this argument, as he understood it, presupposes certain views about movement and physical change that may not be accepted today, it does make the main point that finite processes call for some ground or condition other than themselves.
This becomes more explicit in the second way, which proceeds from the principle that everything must have an "efficient cause"--i.e., a cause that actively produces and accounts for it--to the notion of a
first cause required to avoid an infinite regress, or tracing of causes endlessly backward. As normally found, the idea of efficient causality, in respect to change and process, has many difficulties; and some would prefer to speak instead of regular or necessary sequence. But a more serious objection stresses the apparent inconsistency of thinkers who invoke a general principle of causality and then exempt the alleged first cause. As the child is apt to put it, "Who then made God?" To this a defender of St. Thomas, or at least of the present approach to the idea of God, would reply that the first cause is not supposed to be itself a member of any ordinary causal sequence but altogether beyond it, an infinite reality not itself a part of the natural or temporal order at all. This point, in fact, is what the third way, starting from the
contingency of the world, brings out more explicitly. Nothing explains itself, and all other explanations fall short of showing in any exhaustive way why anything is as it is, or why there is anything at all. But it is also hard to suppose that things just happen to be. Nothing could come out of just nothing, and so the course of events as men find and explain them points to some reality that is not itself to be understood or explained in the normal way at all: it is Explanation with a capital E, as it were, that is seen to be necessitated by all that there is--of whose nature, however, nothing may be directly discerned beyond the inevitability of its being as the ultimate or unconditioned ground of all else and in this way transcendent or utterly mysterious in itself.
This way of thinking of the being and necessity of God has been impressively presented in the mid-20th century by notable thinkers like Austin Farrer, E.L. Mascall, and H.P. Owen and also by the present writer (see below
Bibliography). Generally known as the cosmological approach to the idea of God, it has much in common with the insistence on the transcendence of God in recent theology.
Scholars have often converged upon the same theme in what appears to be a very different line of argument, namely the ontological one, with which are associated especially the names of St. Anselm, first of the Scholastic philosophers (in the 11th century), and
René Descartes, first major modern philosopher (in the mid-17th century). Proponents of this argument try to show that the very idea of God implies his existence. God is the greatest or most perfect being. If the attribute of existence, however, is not included in man's concept of God, he can then think of something more perfect, viz., that which has existence as well. Critics, such as
Gaunilo--a monk of Marmoutier--in Anselm's day and Immanuel Kant--one of the major architects of modern philosophy--many centuries later, have fastened on the weakness that existence is not a predicate or attribute in the same way, at least, as colour or shape; but there have been highly ingenious attempts by influential religious thinkers of today to restate the argument in an acceptable form. (See especially the writings of Charles Hartshorne and Norman Malcolm.) Others find in the argument an oblique and needlessly elaborate way of eliciting the feeling that there must be some reality that exists by the very necessity of its own nature and to which everything else directs man's thought.