In the first place it is to be observed, that Aristotle’s positions on this subject are unmixed with fiction. The wise Stagyrite speaks of no successive particles propagating motion like billiard balls, as Hobbes; nor of nervous or animal spirits, where inanimate and irrational solids are thawed down, and distilled, or filtrated by ascension, into living and intelligent fluids, that etch and re-etch engravings on the brain, as the followers of Des Cartes, and the humoral pathologists in general; nor of an oscillating ether which was to effect the same service for the nerves of the brain considered as solid fibres, as the animal spirits perform for them under the notion of hollow tubes, as Hartley teaches--nor finally, (with yet more recent dreamers) of chemical compositions by elective affinity, or of an electric light at once the immediate object and the ultimate organ of inward vision, which rises to the brain like an Aurora Borealis, and there, disporting in various shapes,--as the balance of plus and minus, or negative and positive, is destroyed or re-established,--images out both past and present. Aristotle delivers a just theory without pretending to an hypothesis; or in other words a comprehensive survey of the different facts, and of their relations to each other without supposition, that is, a fact placed under a number of facts, as their common support and explanation; though in the majority of instances these hypotheses or suppositions better deserve the name of upopoiaeseis, or suffictions. He uses indeed the word kinaeseis, to express what we call representations or ideas, but he carefully distinguishes them from material motion, designating the latter always by annexing the words en topo, or kata topon. On the contrary, in his treatise De Anima, he excludes place and motion from all the operations of thought, whether representations or volitions, as attributes utterly and absurdly heterogeneous.