[137] Come, and at once abandoning all other things, learn to know yourselves, and tell us plainly what ye yourselves are in respect of your bodies, in respect of your souls, in respect of your external senses, and in respect of your reason. Tell us now with respect to one, and that the smallest, perhaps, of the senses, what sight is, and how it is that you see; tell us what hearing is, and how is it that you hear; tell us what taste is, what touch is, what smell is, and how it is that you exercise the energies of each of these faculties; and what the sources of them are from which they originate.