Book 4
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THALES first pronounced that the soul is that being which is in a perpetual motion, or that whose motion proceeds from itself. Pythagoras, that it is a number moving itself; he takes a number to be the same thing with a mind. Plato, that it is an intellectual substance moving itself, and that motion is in a numerical harmony. Aristotle, that it is the first actuality (ἐντελέχεια) of a natural organical body which has life potentially; and this actuality must be understood to be the same thing with energy or operation. Dicaearchus, that it is the harmony of the four elements. Asclepiades the physician, that it is the concurrent exercitation of the senses.
Chapter III. WHETHER THE SOUL BE A BODY, AND WHAT IS THE NATURE AND ESSENCE OF IT.
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ALL those that have been named by me do affirm that the soul itself is incorporeal, and by its own nature is in a perpetual motion, and in its own essence is an intelligent substance, and the actuality of a natural organical body which has life. The followers of Anaxagoras, that it is airy and a body. The Stoics, that it is a hot breath. Democritus, that it is a fiery composition of things which are perceptible by reason, the same having their forms spherical and without an inflaming faculty; and it is a body. Epicurus, that it is constituted of four qualities, of a fiery quality, of an aerial quality, a pneumatical, and of a fourth quality which hath no name, but it contains the virtue of the sense. Heraclitus, that the soul of the world is the exhalation which proceeds from the moist parts of it; but the soul of animals, arising from exhalations that are exterior and from those that are within them, is homogeneous to it.
Chapter IV. OF THE PARTS OF THE SOUL.
