mainly is the psychological process of thinking) or — in more complicated cases — we use written signs = figures and numbers in drawings and calculations or perhaps even little models (especially in the case of technical inventions). As nearly everywhere else, words play a great part here, they are helpful signs both in gaining knowledge, and in communicating it. So what happens when we acquire knowledge or cognition of a fact is this: we reduce it mentally to some other thing or things with which we are already acquainted, and this "reduction" is simply a description of the new object by means of the same signs that described the old objects. In this way the "unknown" is made "known".
Whatever other case we may examine — in all genuine knowledge we find as a common feature an act of recognition which enables us to describe the object of it by means of signs that are used also on other occasions.
Now this activity of finding similarities between things which at first sight do not seem to have anything in common has gradually become a pleasure in itself. The process of acquiring knowledge, at first nothing but an indispensable means of mastering things and situations for the purposes of life, has had the same fate as other useful activities: as walking developed into dancing, speaking into singing, so the pursuit of knowledge developed into science. The human mind takes a delight in reducing things to one another, man enjoys this game, no matter whether he can derive any practical advantage from it or not.
Every progress in scientific knowledge is the discovery of a new description of a thing or process, a description in terms of something else. The chemist describes water as a particular compound of oxygen and hydrogen, he does not need the word "water" any more and can always write the combination of signs H2O instead. The physicist discovers similarities between all the different chemical "elements" which enable him to describe them as combinations of "protons" and "electrons", thereby reducing the number of necessary symbols from 92 to 2; he describes all the properties of light, of radiating heat, of Roentgen rays and of radio waves in terms of the electromagnetic properties of "photons".
It must not be supposed that this scheme is restricted to sciences in the narrower sense of the word; the historian, the linguist, the worker in the
