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CH. II.] immortals, and that this resemblance is manifested by its being continuously in motion; for all divine bodies, he argues, the moon, sun, stars, and heavens, are continuously moving.

Some writers of smaller pretension—and Hippo was one of them—have ventured to represent the Vital Principle as water; and they seem to have been led to this persuasion by the nature of semen, which, in all creatures, is fluid. Hippo, indeed, reproves those who assert that the Vital Principle is blood, because blood is not semen; and semen is, according to him, the first principle of life.

Others have maintained, as did Critias, that the Vital Principle is blood, from their assuming that the most peculiar property of blood is feeling, and that feeling is imparted to us through the nature of blood. All the elements, in fact, have had their partisans, excepting earth; and no one has adopted it, unless such an opinion may be attributed to those who have derived the Vital Principle from all, or made it to be all the elements.

Thus, all these philosophers define Vital Principle by the three properties, motion, feeling, and incorporeity, each of which is referrible to first causes. Such of them, therefore, as define it by the faculty of knowing, make it to be an element or a derivative from the elements, and, with one exception, their opinions coincide;—for they all maintain that like is