After the discovery by Galileo of the parallelogram of forces, it became the object of classical physics - unexpressed, indeed, until Newton wrote his Principia - to bring the unchanging laws ruling nature into the light of human consciousness, and to give them conceptual expression in the language of mathematical formulae. Since, however, science was obliged to restrict itself to what could be observed with a single, colour-blind eye, physics has taken as its main object of research the spatio-temporal relationships, and their changes, between discrete, ideally conceived, point-like particles. Accordingly, the mathematically formulable laws holding sway in nature came to mean the laws according to which the smallest particles in the material foundation of the world change their position with regard to each other. A science of this kind could logically maintain that, if ever it succeeded in defining both the position and the state of motion, in one single moment, of the totality of particles composing the universe, it would have discovered the law on which universal existence depends. This necessarily rested on the presupposition that it really was the ultimate particles of the physical world which were under observation. In the search for these, guided chiefly by the study of electricity, the physicists tracked down ever smaller and smaller units; and along this path scientific research has arrived at the following peculiar situation.