A man's knowledge may be said to be mature, in other words, when it has reached the most complete state of perfection to which he, as an individual, is capable of bringing it, when an exact correspondence is established between the whole of his abstract ideas and the things he has actually perceived for himself. His will mean that each of his abstract ideas rests, directly or indirectly, upon a basis of observation, which alone endows it with any real value; and also that he is able to place every observation he makes under the right abstract idea which belongs to it.

True brevity of expression consists in a man only saying what is worth saying, while avoiding all diffuse explanations of things which every one can think out for himself.

Monotheistic religions alone furnish the spectacle of religious wars, religious persecutions, heretical tribunals, that breaking of idols and destruction of images of the gods, that razing of Indian temples and Egyptian colossi, which had looked on the sun 3,000 years: just because a jealous god had said, Thou shalt make no graven image.

The life of every individual is really always a tragedy, but gone through in detail, it has the character of a comedy.

The greatest intellectual capacities are only found in connection with a vehement and passionate will.

Motives are causes experienced from within.

If anyone spends almost the whole day in reading...he gradually loses the capacity for thinking...This is the case with many learned persons; they have read themselves stupid