There are many justifications of silence; there can be none of insincerity.

Metaphysical ghosts cannot be killed, because they cannot be touched; but they may be dispelled by dispelling the twilight in which shadows and solidities are easily confounded. The Vital Principle is an entity of this ghostly kind; and although the daylight has dissipated it, and positive Biology is no longer vexed with its visitations, it nevertheless reappears in another shape in the shadowy region of mystery which surrounds biological and all other questions.

We must never assume that which is incapable of proof.

The true function of philosophy is to educate us in the principles of reasoning and not to put an end to further reasoning by the introduction of fixed conclusions.

Genius is rarely able to give any account of its own processes.

There are many justifications of silence; there can be none of insincerity.

In complex trains of thought signs are indispensable.