Two kinds of explanation

In 1957 Elizabeth Anscombe published a groundbreaking book in the philosophy of action called Intention. Partly inspired by Wittgenstein and partly inspired by Aristotle, she sought to provide an outward-looking account of action. She started off by asking the question: what distinguishes actions that are intentional from those that are not? Her answer was: “that they are the actions to which a certain sense of the question ‘Why?’ is given application; the sense is of course that in which the answer, if positive, gives a reason for acting” (1957: 9). Although Anscombe did not put it as bluntly as this, the idea is that what makes action stand out from other natural phenomena is that the explanation of what someone did in some weak sense justifies what they did at the same time.

Suppose you want to know why a certain liquid dissolved some salt. The explanation may include the fact that salt ionizes in such a liquid. This provides a reason of sorts. We do say that the reason why the liquid dissolved the salt is that the salt ionizes in such a liquid. But, of course, this is not a reason for the liquid; the liquid's action is not thereby justified.

Knowing the reason why the salt dissolved makes it intelligible to us. We understand why something happens when we know the causal explanation of its happening. And the reasonwhy the salt dissolved forms part of its causal explanation. But there are different kinds of intelligibility. What I want to understand when I see someone waving a flag is a different kind of thing from what I want to understand when I see a liquid dissolving some salt.