The person who doubts there is an external world does not need proof: he needs a cure.

There are two great classes of men: the people and the scholars, the men of science. For the former, nothing exists but that which directly leads to action. It is for the latter to see beyond. They are the free artists who create the future and its history, the conscious architects of the world.

Nothing is more destructive of individual character than for a man to lose all faith in his own abilities for the prosecution of his work.

What sort of philosophy one chooses depends, therefore, on what sort of man one is; for a philosophical system is not a dead piece of furniture that we can reject or accept as we wish; it is rather a thing animated by the soul of the person who holds it.

Upon the progress of knowledge the whole progress of the human race is immediately dependent: he who retards that, hinders this also.

Humanity may endure the loss of everything; all its possessions may be turned away without infringing its true dignity - all but the possibility of improvement.

A man can do what he ought to do; and when he says he cannot, it is because he will not.