If man were forced to demonstrate to himself all the truths of which he makes daily use, his task would never end.

He would exhaust his strength in preparatory exercises, without advancing beyond them.

As, from the shortness of his life, he has not the time, nor, from the limits of his intelligence, the capacity, to accomplish this, he is reduced to take upon trust a number of facts and opinions which he has not had either the time or the power to verify himself, but which men of greater ability have sought out, or which the world adopts.

On this groundwork he raises for himself the structure of his own thoughts; nor is he led to proceed in this manner by choice so much as he is constrained by the inflexible law of his condition.

There is no philosopher of such great parts in the world, but that he believes a million of things on the faith of other people, and supposes a great many more truths than he demonstrates.