It seems to me farther, that these particles have not only a vis inertiae, accompanied with such passive laws of motion as naturally result from that force, but also that they are moved by certain active principles, such as that of gravity, and that which causes fermentation, and the cohesion of bodies. These principles I consider, not as occult qualities, supposed to result from the specific forms of things, but as general laws of nature, by which the things themselves are form'd; their truth appearing to us by phaenomena, though their causes be not yet discover'd. For these are manifest qualities, and their causes only are occult.

Isaac Newton

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