Why does causality work? (OR: What is change?) Modern physics offers a powerfully sophisticated description of the behaviour of matter, including extremely complex maths that gives us highly reliable predictive power.
But, when you peel back the layers of that onion, what you find are wispy metaphors and “placeholder” terms at the core. The most popular, of course, are the terms “energy” and “force”. But, what is that? The common example of billiard balls provides a good illustration. Setting aside how the motion came to be in the first place, for discussion’s sake, imagine that one ball strikes another. The other ball, of course, itself begins to move. Physics calls this a transference of kinetic energy, but all this means in plain terms, is that ball A gave ball B the ability to do the work of motion.
In the Physics, Aristotle says that we aim at understanding, which he says is to be able to give a full account of “the how and the why of things coming into existence and going out of it”. In other words, to understand something is to be able to give an explanation of how and why a thing changes. That explanation is what Aristotle means by ‘cause’. Today, thinking of explanation in terms of causes is not an alien notion. But, when we do this, we are typically only thinking in one narrow scientific sense of the term. Aristotle, however, describes a theory of causal explanation in both the Physics and the Metaphysics that includes four separate categorical senses of the term. Aristotle insists that a complete explanation will appeal to all four of these kinds of cause. In this answer, I will briefly describe the four causes, and attempt to explain why the fourth, ‘final’ cause is primary in Aristotle’s theory.
