and not artificial. At all events, an image is contemplated in a different light by a man skilful in art, from that in which it is viewed by a man ignorant of art.
By sensation, the Stoics understand a species of breath which proceeds from the dominant portion of the soul to the senses, whether it be a sensible perception, or an organic disposition, which, according to the notions of some of them, is crippled and vicious. They also call sensation the energy, or active exercise, of the sense. According to them, it is to sensation that we owe our comprehension of white and black, and rough and smooth: from reason, that we derive the notions which result from a demonstration, those for instance which have for their object the existence of Gods, and of Divine Providence. For all our thoughts are formed either by indirect perception, or by similarity, or analogy, or transposition, or combination, or opposition. By a direct perception, we perceive those things