When an object such as a fruit, a leaf, or a flower changes its color, this means that it has begun to vibrate at a different rate; and when an object changes its savoir, turning from sour to sweet or from sweet to bitter, this also means that it is changing from one rate of vibrations to another. It is a well-known fact, too, that between cold and heat all the different degrees are nothing but changes of vibrations which make things feel cold or hot to us; and it is also by the change of vibrations that the fragrance of flowers and fruit changes. A ripe fruit smells different from the fruit which is not yet ripe, and the quality of the fruit also can be distinguished by the sense of smell through the medium of vibrations. This shows that all things that we perceive through our five senses become intelligible to us, and we are able to distinguish them, by feeling the different degrees of vibrations through our senses. We give names to this phenomenon of vibration: sweet, sour, or salt; green, blue, or red; cold, warm, or hot; because the purpose of each sense is to feel that particular phenomenon of vibrations which is related to it, the eyes seeing, the ears hearing, and the nose smelling.