None of our sensations, if isolated, could have brought us to the concept of space; we are brought to it solely by studying the laws by which those sensations succeed one another.

Every age has scoffed at its predecessor, accusing it of having generalized too boldly and too naïvely. Descartes used to commiserate the Ionians. Descartes in his turn makes us smile, and no doubt some day our children will laugh at us.

The [usual convention] is the belief in continuity, a belief without which it would be difficult to justify apodeictic reasoning, but without which all science would be impossible.