Though there is a strictly logical aspect to negation, there is also a huge pragmatic component that cannot be predicted from the logic: negatives in natural language are shown to be presuppositionally marked (presupposing an error on the part of the hearer) in that they are uttered in a context in which the corresponding affirmatives (which only presuppose the hearer's ignorance) have already been discussed or in which the speaker assumes the hearer's belief in the corresponding affirmatives. The ontology of negation in language is said to be grounded in the perceptual principle of figure-ground.