The Crusades - the most signal and most durable monument of human folly that has yet appeared in any age or nation.

In our reasonings concerning matter of fact, there are all imaginable degrees of assurance, from the highest certainty to the lowest species of moral evidence. A wise man, therefore, proportions his belief to the evidence.

Examine the religious principles which have, in fact, prevailed in the world. You will scarcely be persuaded that they are other than sick men's dreams.

Disbelief in futurity loosens in a great measure the ties of morality, and may be for that reason pernicious to the peace of civil society.

The sweetest path of life leads through the avenues of learning, and whoever can open up the way for another, ought, so far, to be esteemed a benefactor to mankind.

In this sullen apathy neither true wisdom nor true happiness can be found.

While Newton seemed to draw off the veil from some of the mysteries of nature, he showed at the same time the imperfections of the mechanical philosophy; and thereby restored her ultimate secrets to that obscurity, in which they ever did and ever will remain.