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24 the properties both of knowing and imparting motion, as he maintains that it is the mind which has given motion to the universe.

Thales, too, from what has been recorded of him, seems to have assumed that the Vital Principle is something motive, since he said that the loadstone must have a Vital Principle because it gives motion to iron.

Diogenes, together with some other writers, held the Vital Principle to be air, because air was believed to be the most attenuated of the elements, as well as an originating cause; and that, through these properties, the vital principle is able both to recognise things and to impart motion to them. They argued that Vital Principle, as being a first cause and the origin of other things, is able to recognise them; and that, as being the most attenuated of entities, it is motive.

Heraclitus also maintains that the Vital Principle is a first cause, since, in his system, it is the exhalation out of which he constitutes every thing else ; he regards it too as the most incorporeal of entities, and as being "in a constant state of flux;" and further says, that the moved must be known to the motor. He agreed, in fact, with most others in believing all things to be in motion.

The opinions of Alcmaeon upon the Vital Principle seem to be very like those just cited—for he says that it is immortal, on account of its resemblance to the