Parmenides adds to this doctrine of the truth, the doctrine of human opinions, the illusive system of the world. Simplicius, writing on Aristotle’s Physics (p. 7 b; 39 a), tells us that he says: “Men have two forms of opinion, one of which should not be, and in it they are mistaken; they set them in opposition to one another in form and symbol. The one, the ethereal fire of the flame, is quite fine, identical with itself throughout, but not identical with the other, for that is also for itself; on the other hand there is what belongs to night, or thick and ponderous existence.” By the former, warmth, softness, lightness is expressed, and by the latter, cold. “But since everything is called light and night, and their qualities are suited both to the one kind of things and the other, everything alike is filled with light and dark night; both are alike since nothing exists without both.” Aristotle (Met. I. 3 and 5), and the other historians, likewise unanimously attribute to Parmenides the fact that he sets forth two principles for the system of manifest things, warmth and cold, through the union of which everything is. Light, fire, is the active and animate; night, cold, is called the passive. Parmenides also speaks like a Pythagorean—he was called _ἀνὲρ Πυθαγορεῖος_ by Strabo—in the following, and likewise mythological conception: “There are circlets wound round one another, one of which is of the rare element and the other of the dense, between which others are to be found, composed of light and darkness mingled. Those which are less are of impure fire, but those over them of night, through which proceed the forces of the flames. That which holds this all together, however, is something fixed, like a wall, under which there is a fiery wreath, and the most central of the rare spheres again is fiery. The most central of those mixed is the goddess that reigns over all, the Divider (_κληροῦχος_), Dice and Necessity. For she is the principle of all earthly produce and intermingling, which impels the male to mix with the female, and conversely; she took Love to help her, creating him first amongst the gods. The air is an exhalation (_ἀναπνοή_) of the earth; the sun and the milky way, the breath of fire; and the moon is air and fire mingled, &c.”[54] It still remains to us to explain the manner in which Parmenides regarded sensation and thought, which may undoubtedly at first sight seem to be materialistic. Theophrastus,[55] for example, remarks in this regard: “Parmenides said nothing more than that there are two elements. Knowledge is determined according to the preponderance of the one or of the other; for, according as warmth or cold predominate, thought varies; it becomes better and purer through warmth, and yet it requires also a certain balance.”