[51] And what is meant by this I will explain more distinctly: a flavour is appreciable by the sight, not inasmuch as it is flavour, but so far as it is a mere substance, for in so far as it is flavour the sense of taste will judge of it; again a smell, in so far as it is a smell, will be decided upon by the nostrils, but inasmuch as it is a bodily substance, it will also be judged of by the eyes: and the other objects of sense will be tested in this manner; but voice is not appreciable by the sense of sight, neither inasmuch as it is a body, if indeed it is a body at all, nor inasmuch as it can be heard; but there are these two things in us which are wholly invisible—mind and speech;