  As with On Signs, what remains of a badly damaged treatise on the senses attributed to Philodemus (PHerc. 19/698, ed. Monet 1996) takes the Epicurean theory of perception, with its description of the atomic basis of the senses and their irrationality, as a background against which to discuss developments of the theory due to the confrontation with opponents, in this instance Stoics and Aristotelians. Of special concern are: the unity of sensation (I-VIII) and the ‘common sense’ (XX-XXVII) as opposed to the particular objects of each sense (XXVIII-XXIX); and the rejection of Stoic ‘grasping’ (katalêpsis) once one admits the Epicurean theory of ‘affection’ (pathos), which includes both perceiving and perceiving that one is perceiving (IX-XVII).