Le cerveau du savant, qui n'est qu'un coin de l'Univers, ne pourra jamais contenir l'univers tout entier - Henri Poincaré

the sum of the angles of a triangle is equal to two right angles; but this is because the triangles we deal with are too little; the difference, according to Lobachevski, is proportional to the surface of the triangle; will it not perhaps become sensible when we shall operate on larger triangles or when our measurements shall become more precise? The Euclidean geometry would thus be only a provisional geometry.

Correlative movement' therefore constitutes the sole connection between two phenomena which otherwise we never should have dreamt of likening.

Mathematicians do not deal in objects, but in relations between objects; thus, they are free to replace some objects by others so lone as the relations remain unchanged. Content to them is irrelevant; they are interested in form only.