Four causes (αἰτία, aitía) — Aristotle’s doctrine that to know something is to know it through its causes, and that the answers to the question “why?” are of four kinds. The Greek word aitía means “cause,” but also “responsibility” and “explanation,” and interpreters often note that its sense is wider than “cause” in modern usage. The doctrine is set out in the Physics (II.3, 194b16–195a3) and the Metaphysics (V.2, 1013a24–b3), and the requirement of knowing through causes appears in the Posterior Analytics. The four are: the material cause (hylē), that out of which something is made, such as the bronze of a statue; the formal cause (eidos, the essence or definition), what the thing is, such as the statue’s form; the efficient cause (that from which the beginning of motion or change comes), such as the sculptor; and the final cause (telos, “that for the sake of which”), such as health, which is the end of walking. A single thing may have several causes, and one cause may produce opposite effects. In the Physics (II.7, 198a), Aristotle observes that in natural beings the formal, efficient and final causes often coincide. The theory underpins his physics and biology, in which nature acts for the sake of an end, and it is tied to hylomorphism. The Scholastics, such as Thomas Aquinas, inherited it; in modern science, with Francis Bacon and others, the word “cause” tended to be restricted to efficient cause, and Hume’s critique targeted it. See also telos, eidos, ousia, dynamis and energeia and physis; Aristotle, Thomas Aquinas and Hume.
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