XLVI. (190) Some one will say, We at once comprehend colours. How so? Do we not do so by means of the external things, air and light, and also by the moisture which exists in our eyes themselves? And in what way are sweet and bitter comprehended? Is it apart from the moisture in our mouths? And as to all the flavours which are in accordance with, or at variance with nature, are not they in the same case? What, again, are we to say of the smells arising from perfumes which are burnt? Do they exhibit plain unmixed simple natures, or rather qualities compounded of themselves and of the air, and sometimes also of the fire which consumes their bodies, and also of the faculty existing in our own nostrils? (191) From all this we collect the inference that we have neither any proper comprehension of colours, not only of the combination which consists of the objects submitted to our view and of light; nor of smells, but only of the mixture which consists of that which flows from substances and the all-receiving air; nor of tastes, but only of the union which arises from the tasteable object presented to us, and the moist substance in our mouths.