THREE:The force of gravity acts only in one directionvertically, so that the main force of hoisting and handling machinery which opposes gravity must also act vertically, while the horizontal movement of objects may be accomplished by simply overcoming the friction between them and the surfaces on which they move. This is seen in practice. A force of a hundred pounds may move a loaded truck, which it would require tons to lift; hence the horizontal movements of material may be easily accomplished by hand with the aid of trucks and rollers, so long as it is moved on level planes; but if a weight has to be raised even a single inch by reason of irregularity in floors, the difference between overcoming frictional contact and opposing gravity is at once apparent.Descartes theory of the universe included, however, something more than extension (or matter) and motion. This was Thought. If we ask whence came the notion of Thought, our philosopher will answer that it was obtained by looking into himself. It was, in reality, obtained by looking into Aristotle, or into some text-book reproducing his metaphysics. But the Platonic element in his system enabled Descartes to isolate Thought much more completely than it had been isolated by Aristotle. To understand this, we must turn once more to the Timaeus. Plato made up his universe from space and Ideas. But the Ideas were too vague or too unintelligible for scientific purposes. Even mediaeval Realists were content to replace them by Aristotles much clearer doctrine of Forms. On the other hand, Aristotles First Matter was anything but a satisfactory conception. It was a mere abstraction; the390 unknowable residuum left behind when bodies were stripped, in imagination, of all their sensible and cogitable qualities. In other words, there was no Matter actually existing without Form; whereas Form was never so truly itself, never so absolutely existent, as when completely separated from Matter: it then became simple self-consciousness, as in God, or in the reasonable part of the human soul. The revolution wrought by substituting space for Aristotles First Matter will now become apparent. Corporeal substance could at once be conceived as existing without the co-operation of Form; and at the same stroke, Form, liberated from its material bonds, sprang back into the subjective sphere, to live henceforward only as pure self-conscious thought.
A human being is a part of a whole, called by the magic and know universe.