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moment. The forms or ideas of a Plato or an Aristotle correspond to privileged or salient moments in the history of things—the very same moments, generally speaking, that have been fixed by language. They are supposed, like the infancy and old age of a living being, to characterize and express the quintessence of a period, all the remainder of which is filled with the transition from one state to another, and is, therefore, devoid of interest in itself. Consider, for example, the falling of a body. It was thought to be a sufficient account of the fact when it had been characterized summarily as a movement downward, a tendency towards a center, the natural movement of a body, which, after being separated from the earth to which it belongs, returns again to its original position. Therefore, the final or culminating point (Τέλος άκμή) of a process is singled out and is erected into an essential moment, and science is satisfied with this moment, which language has seized upon for the purpose of expressing the ensemble of the fact. In the physics of Aristotle, the movement of a body hurled through space, or freely falling, is defined by concepts of above and below, of spontaneous and enforced displacement, of proper and improper position. But Gallilei believed that there was no essential moment, no privileged instant; in his opinion one should be able to give an account of a falling body at any moment in its course, for that is the true science of gravitation which determines the position of a body in space at any instant of time. For this purpose we, of course, need more precise symbols than those of language.

To Aristotle we may also turn for a biological illustration of the differences between ancient and modern scientific observation. According to his conception, the type or privileged moment of humanity is represented by the adult male individual, with reference to whom youth and age are merely incipient and declining stages respectively, and woman is merely an abortive attempt on the part of nature to produce a man. Contrast with this our present biological conception of the sexes and the ontogeny of the human species!

It must be admitted that the tendency of modern science is in the direction of much greater refinement on the ancient method, a tendency to scrutinize more humbly and more closely, and hence, to multiply indefinitely the observed moments and aspects. I, therefore, do not use the term "ancient" in the sense of "no longer existing," since the tendency thus designated is still constantly manifested in all our ordinary thinking. To observe and retain only the privileged moments and aspects of things is for very many purposes eminently practical, but it has its disadvantages, for the more such moments of an object are accentuated or exalted, the more insignificant or debased become its other aspects. Such emphasis may be highly artistic, but it is contrary to the spirit of modern science. Indeed, much of the lack of sympathy that exists between men of extremely artistic and extremely scientific temperament is due to this difference of instinctive attitude towards the world of phenomena.

It is well known that in their development the biological have