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dently of all other objects, and which are supposed to be representable in the sensations of the human eye. The notion of such properties is a contradiction in itself. They cannot possibly exist, and therefore we cannot expect to find any coincidence of our sensations of color with qualities of light."

The fundamental truth which is implied in these sentences is of such transcendent importance that it is hardly possible to be too emphatic in its statement, or too profuse in its illustration. All quality is relation; all action is reaction; all force is antagonism; all measure is a ratio between terms neither of which is absolute; every objectively real thing is a term in numberless series of mutual implications, and its reality outside of these series is utterly inconceivable. A material entity, absolute in any of its aspects, would be nothing less than a finite infinitude. There is no absolute material quality, no absolute material substance, no absolute physical unit, no absolutely simple physical entity, no absolute constant, no absolute standard either of quantity or quality, no absolute motion, no absolute rest, no absolute time, no absolute space. There is no physical thing, nor is there a real or conceptual element of such a thing, which is either its own support or its own measure, and which abides either quantitatively, or qualitatively, otherwise than in perpetual change, in an unceasing flow of mutations. An object is large only as compared with another which, as a term of this comparison, is small, but which, as a term in a comparison with a third object, may be indefinitely large; and the comparison which determines the magnitude of objects is between its terms alone, and not between any or all of these terms, and an absolute standard. An object is hard as compared with another which is soft, but which, in turn, may be contrasted with a third still softer; and, again, there is no standard object which is either absolutely hard or absolutely soft. A body is simple as compared with the compound into which it enters as a constituent; but there is, and can be no physically real thing which is absolutely simple. Similarly, all changes of position or distance between two bodies are wholly relative, and it is a matter of purely arbitrary determination, which of them is taken as being at rest, and which as in motion. It is equally true to say that the earth falls toward the apple, and that the apple falls toward the earth.

I may observe, in this connection, that not only the law of causality, the persistence of force, and the indestructibility of matter, have their root in the relativity of all objective reality—being, indeed, simply different aspects of this relativity—but that Newton's first and third laws of motion, as well as all laws of least action, so called, in mechanics (including Gauss's law of movement under least coercion), are but corollaries from the same principle. And the fact that every thing is, in its manifest existence, but a group of relations and reactions, at once accounts for Nature's inherent teleology.