Kant claimed that pleasure and displeasure (pain) were complementary: both were expressions of the same ‘feeling of pleasure and pain’. In A he describes them as ‘opposed to each other, not like gain and deficiency (+ or 0), but like gain and loss (= and −), that is, one is not contrasted with the other merely as an opposite (contradictorie, sive logice oppositum), but rather as a counterpart (contrarie sive realiter oppositum)’ (A §60). Kant maintains that beyond claiming that pleasure and displeasure are counterparts of the same subjective feeling, they ‘cannot be explained more clearly in themselves; instead, one can only specify what results they have in certain circumstances’ (MM p. 212, p. 41). One of these results follows from whether the feeling incites the subject to abandon or maintain a particular state; another consists in the tendency of pleasure to enhance the feeling of life, and of displeasure or pain to hinder it (A §60). Both however are necessary to each other: without the check of displeasure, the steady advancement of vitality accompanying pleasure would result in a ‘quick death’. In A Kant distinguishes between sensuous and intellectual pleasure and displeasure, subdividing the former according to whether the pleasure/displeasure is caused by sensation or imagination, and the latter ...
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