Change, motion, and explanation › Four ways to answer why

In Physics II.3, Aristotle distinguishes four senses of cause. The Greek term translated as cause has an explanatory range broader than the familiar question of which event immediately triggered another. The four senses identify different answers to a request for explanation:

1. The material cause is that out of which something comes to be and which remains in it, such as bronze in a statue.
2. The formal cause is the defining account or structure, what makes the thing the kind of thing it is.
3. The source of change, called the efficient cause here, identifies what initiates the relevant making or changing.
4. The final cause is that for the sake of which something happens, such as health explaining why someone takes a walk.

The same thing can have several causes in these different senses. Bronze does not compete with sculptural expertise as an explanation of a statue. They answer different questions. Similarly, the goal of health can explain the decision to exercise without becoming an additional material component of the body (Physics II.3).

Imagine a bowl commissioned for serving soup. Clay answers the material question. The organized shape that makes it a bowl answers the formal question. The potter's skilled activity helps answer the question about its production. Holding soup supplies the stipulated purpose. This is an author-supplied example of an artifact, where an intention makes the final-cause explanation comparatively straightforward.

These should not be pictured as four separate objects attached to every event. In natural generation, Aristotle says the form, the end, and the source of motion often converge: the mature form is an end of development, while another organism of the same form initiates generation (Physics II.7). We still need to identify the explanatory role under discussion, rather than count physically distinct causes.

The framework also distinguishes an intended explanation from a coincidental result. In the discussion of chance, Aristotle considers a person who encounters someone who owes him money and thereby collects a debt, although collecting it was not why he went to that place. The encounter can fall within a purposive activity without itself having been arranged for that purpose (Physics II.4–6). Calling an outcome useful does not establish that it was what the process was for.