Language is a system whose parts can and must all be considered in their synchronic solidarity. - Ferdinand de Saussure

The causes of continuity are a priori within the scope of the observer, but the causes of change in time are not. It is better not to attempt giving an exact account at this point, but to restrict discussion to the shifting of relationships in general. Time changes all things; there is no reason why language should escape this universal law.

The characteristic role of language with respect to thought is not to create a material phonic means for expressing ideas but to serve as a link between thought and sound, under conditions that of necessity bring about the reciprocal delimitations of units. Thought, chaotic by nature, has to become ordered in the process of its decomposition. Neither are thoughts given material form nor are sounds transformed into mental entities; the somewhat mysterious fact is rather that "thought-sound" implies division, and that language works out its units while taking shape between two shapeless masses. Visualize the air in contact with a sheet of water; if the atmospheric pressure changes, the surface of the water will be broken up into a series of divisions, waves; the waves resemble the union or coupling of thought with phonic substance.

Thus we may found the science for the study of the life of signs against the background of social life; it would form part of social psychology, and consequently of general psychology; we shall call it semiology (from Greek sēmeion — 'sign'). That science would explain to us in what signs consist of and by what laws they are governed. Since it is a science which does not yet exist, we do not know what it will be like; it has, however, a reason for its existence, its place is allocated in advance. Linguistics is only a part of that general science ; the laws which semiology will discover, will be applicable also to linguistics, which in turn will be linked with a domain clearly defined throughout the entirety of human affairs.