Five Ways

The Five Ways (Latin Quinque Viae) are Aquinas's five arguments for the existence of God, presented compactly in Summa Theologiae Ia q.2 a.3. Each argument proceeds from an observed feature of the world to a first principle that, Aquinas argues, everyone calls God. The arguments are among the most-discussed in the history of philosophy and the most-engaged single passage in the Thomist corpus.

Definition

The Five Ways are five distinct arguments, each compressed into a few sentences in the Summa Theologiae. They are presented as showing not merely that something divine exists but that the conclusion of each can be identified with what classical theism means by God.

The five arguments

First Way: from motion

Some things are in motion. Whatever is in motion is moved by something else (a thing cannot move itself in the relevant sense). If everything that moves is moved by something else, and the chain of movers is infinite, there is no first mover and therefore no motion. But there is motion. Therefore, there is a first mover, itself unmoved, which everyone calls God.

The argument is recognizably Aristotelian; it depends on Aristotle's account of motion as the actualization of a potency and on the impossibility of an actual infinite regress of essentially ordered causes.

Second Way: from efficient causation

In the world there are efficient causes. Nothing can be the efficient cause of itself. If the chain of efficient causes is infinite, there is no first cause and therefore no later causes and no causation at all. But there is causation. Therefore, there is a first efficient cause, which everyone calls God.

The structure parallels the First Way but applies to efficient causation rather than motion. The argument depends on the same prohibition of infinite regress in essentially ordered causes.

Third Way: from contingency

Some things in the world are contingent (they can be or not be; they come into and go out of existence). If everything were contingent, then at some past time nothing would have existed, and therefore nothing would exist now (because from nothing, nothing comes). But things exist now. Therefore, there must be at least one necessary being. The necessary being's necessity either depends on another or it does not. If on another, there is again the threat of regress. Therefore, there is at least one being necessary in itself, which everyone calls God.

The argument is the most logically complex of the Five Ways and has been the subject of extensive analysis. The relation between temporal and modal readings of contingency is one of the contested interpretive questions.

Fourth Way: from gradation

Things are observed to vary in degrees of perfection (more or less good, more or less true, more or less noble). Any gradation requires a standard against which the gradation is measured — a maximum of the kind. The maximum of being and goodness is what everyone calls God.

The argument is the most distinctly Platonist of the Five Ways, drawing on the doctrine that maxima are the causes of approximations to them in their kind. It is also the most contested in the contemporary discussion; the inference from gradation to a maximum has been pressed by critics from Kant onward.

Fifth Way: from the orderliness of natural processes

Natural things, lacking intelligence, act for ends; this is shown by the fact that they regularly act in the same way for the best outcome. But things lacking intelligence cannot direct themselves toward ends without being directed by something with intelligence. Therefore, there is an intelligent being directing all natural things toward their ends, which we call God.

The Fifth Way is often called the teleological argument and is sometimes confused with later design arguments (Paley's watchmaker analogy). The Thomistic version is structurally different: it depends on the Aristotelian doctrine of final causation and on the claim that final causation requires intelligence as its source.

Common confusions

The Five Ways are not the same as the cosmological argument. Cosmological argument is a contemporary umbrella term for arguments that proceed from the existence or features of the world to God; only the first three Ways are properly cosmological in this sense. The Fourth Way is metaphysical (about gradation of perfection); the Fifth Way is teleological.

The Five Ways are not the same as Paley's design argument. The Fifth Way is not an inference from apparent design to a designer in Paley's later sense. It depends on the prior Aristotelian framework of final causation rather than on the analogy between natural things and artifacts.

The Five Ways are not five steps in a single argument. Each Way is an independent argument; together they offer multiple converging routes to the same conclusion. Aquinas does not present them as five steps of a single demonstration.

The Five Ways do not prove the Christian God in full. Aquinas is explicit (Ia q.2 a.3 in the conclusion of each Way) that the arguments establish only the existence of a first principle and identify it with what everyone calls God. The doctrines of the Trinity, the Incarnation, divine providence in specific cases, and many other distinctly Christian doctrines are not established by the Five Ways and require other arguments or revelation.

Reception

The Five Ways have been continuously discussed since Aquinas. The standard medieval reception integrated them into the broader Scholastic project; the early modern reception was variable, with Cartesian rationalists generally preferring ontological argumentation and empiricists raising specific objections.

David Hume's Dialogues Concerning Natural Religion (1779) attacked the teleological argument generally and through implication the Fifth Way. Kant's Critique of Pure Reason (1781) attacked the entire project of natural theology, arguing that theoretical reason cannot establish the existence of God. The nineteenth century saw the Five Ways largely set aside in Protestant philosophy of religion; they remained central in Catholic philosophy throughout.

The twentieth-century recovery has been substantial. Anthony Kenny's The Five Ways (1969) launched analytic engagement; subsequent work by Brian Davies, Edward Feser, William Lane Craig, and others has developed sophisticated contemporary versions. The new natural theology in analytic philosophy of religion treats the Five Ways as a serious resource rather than a historical curiosity.

Place in the wiki

The Five Ways are a satellite of Natural Law (both belong to the natural-theology project of demonstrating divine truths through reason) and are closely related to the Four Causes (the Aristotelian framework the arguments deploy).

Further reading

• Aquinas — the author
• Summa Theologiae — the central text containing the Five Ways
• Aristotle — the source of the metaphysical framework
• Four Causes — the framework underlying the arguments
• Scholasticism — the tradition
• Anselm — the author of the ontological argument, the rival natural-theological strategy

Satellite of Natural Law. The most-discussed five-argument sequence in the history of philosophy of religion.