 Among the philosophical issues that are important here is the fundamental question of how, if the world is only directly accessibly by perception, can one come to valid knowledge by means of inference that relies on words that do not directly refer to particulars? How does one link the ineffable world of particulars to language, and thus to an inference that could produce valid knowledge? Since words do not apply to actual objects or particulars which are ineffable, Śāntarakṣita, like his predecessors Dharmakīrti and Dignāga, needs to explain how it is that we are talking about the world, while at the same time making it clear that we are not talking about the world, but our conceptual scheme. Yet he also must make clear that all conceptual schemes are not equal in that some can produce valid knowledge and some fail to do so. There must be a degree of non-arbitrariness to language if inference is to be considered as a source of valid knowledge. There are true and false statements and consequences for beliefs about them. So the challenge is: how does one link the ineffable world of particulars to language?