"It is ordinarily believed that human knowledge owes most of its progress to these supreme intellects, which arise from time to time, like miracles of nature.[1] I, on the contrary, think that it owes more to men of common powers than to those who are exceptionally endowed. Suppose a case, in which one of the latter, having rivalled his contemporaries in knowledge, advances independently, and takes a lead of, say ten paces. Most other men, far from feeling disposed to follow him, regard his progress in silence, or else ridicule it. Meanwhile, a number of moderately clever men, partly aided perhaps by the ideas and discoveries of the genius, but principally through their own endeavours, conjointly advance one step. The masses unhesitatingly follow them, being attracted by the not inordinate novelty, and also by the number of those who are its authors. In process of time, thanks to the exertions of these men, the tenth step is accomplished; and thus the opinions of the genius are universally received throughout the civilised world. But their originator, dead long ago, only acquires a late and unseasonable reputation. This is due partly to the fact that he is forgotten, or to the low esteem in which he was held when living; added to which men are conscious that they do not owe their knowledge to him, and that they are already his equals in erudition, and will soon surpass him, if they have not done so already. They are also his superiors, in that time has enabled them to demonstrate and affirm truths that he only imagined, to prove his conjectures, and give better form and order to his inventions, almost, as it were, maturing them. Perchance, after a time, some student engaged in historical research may justly appraise the influence of this genius, and may announce him to his countrymen with great _Èclat_; but the fame that may ensue from this will soon give way to renewed oblivion. "The progress of human knowledge, like a falling weight, increases momentarily in its speed; none the less very rarely men of a generation change their beliefs or recognise their errors, so as to believe at one time the opposite of what they previously believed. Each generation prepares the way for its successor to know and believe many things contrary to its own knowledge and belief. But most men are as little conscious of the increasing development of their knowledge, and the inevitable mutation of their beliefs, as they are sensible of the perpetual motion of the earth. And a man never alters his opinions so as to be conscious of the alteration. But were he suddenly to embrace an opinion totally discordant with his old beliefs, he could not fail to perceive the change. It may therefore be said, that ordinarily no truths, except such as are determinable by the senses, will be believed by the contemporaries of their discoverer."