Socrates begins his enquiry into the essence of perception by asking about the role of the senses, and by extension the body. It would appear that perception is the relation between what is immediately perceivable: smells, colours, sounds etc, and that which is able to take up a perceiving relationship with them. For smells that is the nose, for colour the eyes, etc. Does this mean that it is the body, through the senses, which has a perceptual relationship with what appears? Or is perception only achieved in passing through them, i.e. are the senses just a passageway to perception?
The second characterisation is agreed upon, with Socrates providing the proof: If perceiving was dispersed to different points on the body, so that the eyes are that which see, the ears that which hear etc, what we see and hear, colour and sound, would also be distributed to the corresponding points on the body. This would mean in order to see we would have to direct ourselves to our eyes, in order to hear we would have to direct ourselves to our ears. The end result would be that we could not hear and see something simultaneously.
This is an impossible state of affairs, therefore its opposite is acknowledged, every perception, rather than being dispersed to various points on the body, converges in a unity. This is not a bodily unity, for the body upholds the dispersion of perceiving through its organs of perception. Instead this unity is the “single sighted nature” that we possess, in which all sensory perceptions converge “in something like an idea” [i.e. knowledge, truth]. The idea is what is sighted, it is both seeing and what is seen in its presence, i.e. it is the thing’s essence that is immediately present before us. (126)