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CH. II.] them to be incorporeal; and from these again they differ who make them to be a combination both of corporeal and incorporeal molecules. They differ also with respect to the number of such causes, as some adopt only one while others admit of several; and, in accordance with these conclusions, they form their estimate of the Vital Principle ; but yet they have all assumed, and not unreasonably, that it is of the nature of first causes to be motive. Hence, the Vital Principle has to some appeared to be fire, as fire, besides being the most attenuated and most incorporeal of the elements, is both self-motive and a primal cause of motion in other things.

Democritus has expressed himself more clearly than any other writer in specifying the causes of each of those properties: for he says that the Vital Principle is identical with the mind, and to be placed among primal and indivisible bodies; that it is motive, owing to the tenuity of its parts and its form; that of forms the spherical is the most mobile, and that this is the form both of mind and fire.

Anaxagoras seems, as we have already said, to distinguish the mind from the Vital Principle, although he employs both terms as if synonymous; excepting that he sets down the mind as being, in the fullest sense, the origin of all things. Thus he says that the mind alone of all entities is homogeneous, unmixed, and pure; and to the same principle he attributes