I promised a couple of days ago to talk about Aristotle’s view of causality.

Remember that Aristotle was responding to earlier philosophers, who tended toward two viewpoints: everything is One, and change is an illusion, or everything is in flux, and stability is an illusion. Aristotle brought it down to human scale and noted that we do see things change and we do see things stay the same; and then in his usual fashion thought it all out in extravagant detail. What, he asked, is involved when something changes? He reduced it down to four things, which he called “causes” or “principles” of change.

First, you have to have something to begin with, something that changes. This is called the material cause, or simply the matter. If I throw a ball, the ball is the matter. When an apple changes from green to red, the apple is the matter.

Next, you have to have something that makes the change happen. This is called the effective cause, or sometimes the agent. If I throw a ball, I’m the agent. That’s clear enough. But what about an apple that changes from green to red? It depends. If the apple changes color because I painted it, then clearly I’m the agent. Normally, though, the apple changes from green to red all by itself; it is the apple’s nature to do so, and the apple itself is the agent. In one case, the agent is external, and in the other it is internal. This is part of what it means for something to be natural: it arises out of the thing’s own nature.

Next, there’s how the matter changes, what’s new about it after the change. This is called the formal cause; in Aristotelian terms, the matter receives a new form. Form is not simply shape. When I throw the ball and it rolls into the corner, the ball has a new position; it has the form of being there in the corner, rather than here in my hand. When the apple turns green, it now has the form of greenness.

And finally, no pun intended, there is the final cause, also known as the end. Final causes probably need a whole post to themselves; for now, I’ll simply say that the end is where the process of change stops. As such, it is often the same as the formal cause. Suppose a breeze blows a ball off of the table, and it rolls into the corner. The change ends when the ball stops moving; its new position is the terminus or end. The final cause can also be thought of as the reason for the change: change stops because the desired end state has been reached. But more of that anon.