Five Ways (Aquinas)

"The existence of God may be proved in five ways. The first and most manifest way is the argument from motion. ...Whatever is in motion is moved by another, for nothing can be in motion except it have a potentiality for that toward which it is being moved. ...It is ...impossible that from the same point of view and in the same way anything should be both moved and mover, or that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. This cannot go on to infinity, because then there would be no first mover; as the staff only moves because it is put into motion by the hand. Therefore it is necessary to arrive at a First Mover, put in motion by no other; and this everyone understands to be God."

"A cosmological argument is an argument to the existence of God from the existence of some finite object or, more specifically, a complex physical universe. There have been many versions of the cosmological argument given over the past two-and-a-half millennia; the most quoted are the second and third of Aquinas’s five ways to show the existence of God. However, Aquinas’s ‘five ways’, or rather the first four of his five ways, seem to me to be one of his least successful pieces of philosophy."

"[T]he Five Ways fail […] principally because it is much more difficult than at first appears to separate them from their background in medieval cosmology. Any contemporary cosmological argument would have to be much more different from the arguments of Aquinas than scholastic modernizations customarily are."

"Aquinas believes that human beings (even in our earthly condition here below) can have knowledge, scientific knowledge of God's existence, as well as knowledge that he has such attributes as simplicity, eternity, immateriality, immutability, and the line. In Summa Theologiae Aquinas sets out his famous Five Ways or five proofs of God's existence: in Summa Contra Gentiles he sets out the proof from motion in much greater detail; and in each case he follows these alleged demonstrations with alleged demonstrations that God possesses the attributes just mentioned. So natural knowledge of God is possible. [...] So most of those who believe in God do so on faith. Fundamentally, for Aquinas, to accept a proposition on faith is to accept it on God's authority; faith is a manner of "believing God" (ST, IIa, IIae, ii, 2) "for that which is above reason we believe only because God has revealed it" (SCG, I, 9)."

"Of these ‘ways of being’ of the world around us, noted with greater or lesser understanding, but with equal evidence, by philosophers and common intelligence, there are two that modern science has marvellously explored, ascertained and deepened beyond all expectations:"

"If the primitive experience of the ancients could offer reason sufficient arguments for the demonstration of God's existence, with the broadening and deepening of the field of experience itself, the footprint of the Eternal now shines more brightly and clearly in the visible world. It therefore seems worthwhile to re-examine, on the basis of new scientific discoveries, the classic proofs of the Angelic Doctor, especially those derived from the motion and order of the universe; that is, to investigate whether and to what extent a deeper knowledge of the structure of the macrocosm and microcosm contributes to strengthening philosophical arguments; and then to consider, the other hand, whether and to what extent they have been shaken, as is often claimed, by modern physics having formulated new fundamental principles and abolished or modified ancient concepts whose meaning was perhaps considered fixed and defined in the past, such as time, space, motion, causality and substance, concepts that are extremely important for the question that now concerns us. Rather than a revision of the philosophical proofs, it is therefore a question here of scrutinising the physical bases — and we shall necessarily have to restrict ourselves to only a few, for reasons of time — from which those arguments derive. Nor are there any surprises to be feared: science itself does not intend to leave that world which, today as yesterday, presents itself with those five ‘modes of being’ from which the philosophical demonstration of the existence of God takes its starting point and its strength."