The search for definitions is ubiquitous in Sanskrit philosophy. In many texts across traditions, we find philosophers presenting their theories by laying down definitions of key theoretical categories, by testing those definitions, and by refuting competing definitions of the same theoretical categories. Call this the method of definitions. The aim of this essay is to explore a challenge that arises for this method: the paradox of definitions. It arises from the claim that the method of definitions is either (i) redundant (...) because it does not provide us any knowledge that we did not already possess, or (ii) impossible to successfully pursue because it leads to an infinite regress. Neither of these alternatives should be acceptable to the defender of this method. To focus our discussion, I will show how this challenge arose for—and was arguably resolved by—early Nyāya-Vaiśeṣika thinkers active in the first millennium CE and at the very beginning of the second millennium. In response to the paradox of definitions, these Nyāya-Vaiśeṣika thinkers claimed that the purpose of a definition is to remove either metaphysical ignorance about the distinction between theoretically significant kinds or kind-membership, or metalinguistic ignorance about the meaning or the application-conditions of theoretically significant terms. I will show how this discussion helps us to ward off certain misconceptions about the method of definitions in Nyāya-Vaiśeṣika. (shrink)