If we do this, we might notice that there seem to be only four possible ways to explain (i.e., conceptualize) our objects of consciousness (i.e., our experience). This is so whether our objects are exotic ones, such as photons, or pure mental objects such as the idea of simplicity, or common physical objects such as cups. These four ways form the four horns of Nagarjuna’s tetralemma, which can be simply stated as follows: either (1) objects are themselves, or (2) they are not themselves, or (3) they are both themselves and not themselves, or (4) they are neither themselves nor are they not themselves.It would seem to common sense that at least the first statement ought to hold true, and thus offer some explanation of experience. But, as we shall see, none of the four options does. None does—yet experience remains.
The exposition of that argument is too long to excerpt, but you can read it here, if you've been feeling an urge to pull the epistemological rug out from under your own feet.