Five Ways (Aquinas)
The Quinque viæ (Latin for "Five Ways") (sometimes called "five proofs") are five logical arguments for the existence of God summarized by the 13th-century Catholic philosopher and theologian Thomas Aquinas in his book Summa Theologica. They are:
Aquinas expands the first of these – God as the "unmoved mover" – in his Summa Contra Gentiles.[1]
Background[edit]
Need for demonstration of the existence of God[edit]
Aquinas thought the finite human mind could not know what God is directly, therefore God's existence is not self-evident to us, although it is self-evident in itself.[2] On the other hand, he also rejected the idea that God's existence cannot be demonstrated: although it is impossible to give a so-called propter quid demonstration, going from the causes to the effects; still, the proposition God exists can be "demonstrated" from God's effects, which are more known to us, through a so-called quia demonstration.[3] However, Aquinas did not hold that what could be demonstrated philosophically (i.e. as general revelation) would necessarily provide any of the vital details revealed in Christ and through the church (i.e. as special revelation), quite the reverse. For example, while he would allow that "in all creatures there is found the trace of the Trinity", yet "a trace shows that someone has passed by but not actually who it is."[4]
Categorization[edit]
The first three ways are generally considered to be cosmological arguments.[5] Aquinas omitted various arguments he believed to be insufficient or unsuited, such as the ontological argument made by Anselm of Canterbury.
Sources[edit]
A summary version of the Five Ways is given in the Summa theologiae.[6] The Summa uses the form of scholastic disputation (i.e. a literary form based on a lecturing method: a question is raised, then the most serious objections are summarized, then a correct answer is provided in that context, then the objections are answered).
A subsequent, more detailed, treatment of the Five Ways can be found in the Summa contra gentiles.[1] Aquinas further elaborated each of the Five Ways in more detail in passing in multiple books.
Essential and accidental causal chains[edit]
The first two Ways relate to causation. When Aquinas argues that a causal chain cannot be infinitely long, he does not have in mind a chain where each element is a prior event that causes the next event; in other words, he is not arguing for a first event in a sequence. Rather, his argument is that a chain of concurrent or simultaneous effects must be rooted ultimately in a cause capable of generating these effects, and hence for a cause that is first in the hierarchical sense, not the temporal sense.[7]
Aquinas follows the distinction found in Aristotle's Physics 8.5, and developed by Simplicius, Maimonides, and Avicenna that a causal chain may be either accidental (Socrates' father caused Socrates, Socrates' grandfather caused Socrates' father, but Socrates' grandfather only accidentally caused Socrates) or essential (a stick is moving a stone, because a hand is simultaneously moving the stick, and thus transitively the hand is moving the stone.)[8]
His thinking here relies on what would later be labelled "essentially ordered causal series" by John Duns Scotus.[10] (In Duns Scotus, it is a causal series in which the immediately observable elements are not capable of generating the effect in question, and a cause capable of doing so is inferred at the far end of the chain. Ordinatio I.2.43[11])
This is also why Aquinas rejected that reason can prove the universe must have had a beginning in time; for all he knows and can demonstrate the universe could have been 'created from eternity' by the eternal God.[12] He accepts the biblical
doctrine of creation as a truth of faith, not reason.[8]
For a discussion of a causal chain argument that is based on a created beginning, see Kalam cosmological argument.
Many scholars and commenters caution against treating the Five Ways as if they were modern logical proofs. This is not to say that examining them in that light is not academically interesting.
Reasons include:
Criticism[edit]
Philosophical[edit]
Criticism of the cosmological argument, and hence the first three Ways, emerged in the 18th century by the philosophers David Hume and Immanuel Kant.[34]
Kant argued that our minds give structure to the raw materials of reality and that the world is therefore divided into the phenomenal world (the world we experience and know), and the noumenal world (the world as it is "in itself," which we can never know).[35] Since the cosmological arguments reason from what we experience, and hence the phenomenal world, to an inferred cause, and hence the noumenal world, since the noumenal world lies beyond our knowledge we can never know what's there.[36] Kant also argued that the concept of a necessary being is incoherent, and that the cosmological argument presupposes its coherence, and hence the arguments fail.[37]
Hume argued that since we can conceive of causes and effects as separate, there is no necessary connection between them and therefore we cannot necessarily reason from an observed effect to an inferred cause.[38] Hume also argued that explaining the causes of individual elements explains everything, and therefore there is no need for a cause of the whole of reality.[39][40]
The 20th-century philosopher of religion Richard Swinburne argued in his book, Simplicity as Evidence of Truth, that these arguments are only strong when collected together, and that individually each of them is weak.[41]
The 20th-century Catholic priest and philosopher Frederick Copleston devoted much of his work to a modern explication and expansion of Aquinas' arguments.
More recently the prominent Thomistic philosopher Edward Feser has argued in his book Aquinas: A Beginner's Guide that Richard Dawkins, Hume, Kant, and most modern philosophers do not have a correct understanding of Aquinas at all; that the arguments are often difficult to translate into modern terms.[42] He has defended the arguments in a book at length.[43]
Atheist philosopher J.H. Sobel offers objections to the first three Ways by challenging the notion of sustaining efficient causes and a concurrent actualizer of existence.[44] Atheist philosopher Graham Oppy has offered critiques of the arguments in his exchanges with Edward Feser and in his published work.[45]
Popular[edit]
Biologist Richard Dawkins' book The God Delusion argues against the Five Ways. According to Dawkins, "[t]he five 'proofs' asserted by Thomas Aquinas in the thirteenth century don't prove anything, and are easily [...] exposed as vacuous."[46]
In Why there almost certainly is a God: Doubting Dawkins, philosopher Keith Ward claims that Dawkins mis-stated the five ways, and thus responds with a straw man. For example, for the fifth Way, Dawkins places it in the same position for his criticism as the Watchmaker analogy, when in fact, according to Ward, they are vastly different arguments. Ward defended the utility of the five ways (for instance, on the fourth argument he states that all possible smells must pre-exist in the mind of God, but that God, being by his nature non-physical, does not himself stink) whilst pointing out that they only constitute a proof of God if one first begins with a proposition that the universe can be rationally understood. Nevertheless, he argues that they are useful in allowing us to understand what God will be like given this initial presupposition.[47]
Eastern Orthodox theologian David Bentley Hart says that Dawkins "devoted several pages of The God Delusion to a discussion of the 'Five Ways' of Thomas Aquinas but never thought to avail himself of the services of some scholar of ancient and medieval thought who might have explained them to him ... As a result, he not only mistook the Five Ways for Thomas's comprehensive statement on why we should believe in God, which they most definitely are not, but ended up completely misrepresenting the logic of every single one of them, and at the most basic levels."[48] Hart said of Dawkins treatment of Aquinas' arguments that: