Among epistemologists and philosophers of science, one often hears that someone with understanding is able to “see” or “grasp” how the elements of a subject “cohere” or “fit together”—but just what is involved in the seeing or the grasping is usually left to the imagination. I argue that the most productive way to make progress on this issue is by first identifying the kind of explanation-seeking why-questions that drive the search for understanding in the first place. In particular, I suggest that if we can get a good grip on why a situation stands in need of explanation for us in the first place, then we will in turn be in a good position to determine how we might satisfy that need.
In this respect, I argue that a situation stands in need of explanation for us, and therefore inspires our why-questions, in virtue of our sense that there are various ways that we think the situation might have been. If a situation stands in need of explanation for this reason, moreover, then in order to satisfy the need for explanation our objective will be to identify what the difference between these alternatives depends on.
To say only this much still leaves a great deal underdetermined, however, for we might “identify” what the difference depends on in a number of different ways: for example, by having a true belief about what the difference depends on, by knowing this on the basis of testimony, and so on. What is distinctive about the state of understanding, I suggest, is the particular way in which we identify what the difference depends on: namely, by grasping what the difference depends on. I explore at length what exactly this grasping amounts to.
