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.

No one can be a great thinker who does not recognize that as a thinker it is his first duty to follow his intellect to whatever conclusions it may lead.

There is a very real evil consequent on ascribing supernatural origin to the received maxilms of morality. That origin consecrates the whole of them and protects them from being discussed or criticized.

All political revolutions, not affected by foreign conquest, originate in moral revolutions. The subversion of established institutions is merely one consequence of the previous subversion of established opinions.

The application of algebra to geometry ... has immortalized the name of Descartes, and constitutes the greatest single step ever made in the progress of the exact sciences.

When a thing is bought not for its use but for its costliness, cheapness is no recommendation. As Sismondi remarks, the consequence of cheapening articles of vanity, is not that less is expended on such things, but that the buyers substitute for the cheapened article some other which is more costly, or a more elaborate quality of the same thing; and as the inferior quality answered the purpose of vanity equally well when it was equally expensive, a tax on the article is really paid by nobody: it is a creation of public revenue by which nobody loses.

Human existence is girt round with mystery: the narrow region of our experience is a small island in the midst of a boundless sea. To add to the mystery, the domain of our earthly existence is not only an island of infinite space, but also in infinite time. The past and the future are alike shrouded from us: we neither know the origin of anything which is, nor its final destination.