To mistake money for wealth, is the same sort of error as to mistake the highway which may be the easiest way of getting to your house or lands, for the house and lands themselves.

Both teachers and learners go to sleep at their post as soon as there is no enemy in the field.

Truths are known to us in two ways: some are known directly, and of themselves; some through the medium of other truths. The former are the subject of Intuition, or Consciousness; the latter, of Inference; the latter of Inference. The truths known by Intuition are the original premisses, from which all others are inferred.

Every man who says frankly and fully what he thinks is so far doing a public service. We should be grateful to him for attacking most unsparingly our most cherished opinions.

The peculiarity of the evidence of mathematical truths is that all the argument is on one side.

The duty of man is the same in respect to his own nature as in respect to the nature of all other things, namely not to follow it but to amend it.

...there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered.