From this standpoint the highest Enlightenment is pure perception. Negative perception, perceiving that something is not, has some epistemological relevance but played no logical role in Dharmakirti's system. Enlightenment involves shunyata, the Void, but it is in no sense negative perception. Inference for oneself involves a kind of syllogism in which the reason must meet three requirements. Thus, smoke is in a kitchen, and a kitchen is homologous with things that contain fire.
Smoke never occurs in a lake, which is heterologous with things that contain fire.
Besides having to meet these three conditions, the middle term has to be one of three kinds. Inference for the sake of others requires putting the argument in words acceptable to all concerned, for though words themselves are not knowledge, they can educe it when rightly used. All inference is either affirmation or denial, linking terms in ways which produce statements or theses. A thesis is false if it is incompatible with perception, inference, conception or one's previous statements. Fallacies of the middle term occur when any of the requirements it must meet are unproven, uncertain or contradictory.