It is not reason which is the guide of life, but custom.

Scholastic learning and polemical divinity retarded the growth of all true knowledge.

I shall venture to affirm, that there never was a popular religion, which represented the state of departed souls in such a light,as would render it eligible for human kind, that there should be such a state. These fine models of religion are the mere product of philosophy. For as death lies between the eye and the prospect of futurity, that event is so shocking to nature, that it must throw a gloom on all the regions which lie beyond it; and suggest to the generality of mankind the idea of Cerberus and Furies; devils, and torrents of fire and brimstone.

The difference between a man who is led by opinion or emotion and one who is led by reason. The former, whether he will or not, performs things of which he is entirely ignorant; the latter is subordinate to no one, and only does those things which he knows to be of primary importance in his life, and which on that account he desires the most; and therefore I call the former a slave, but the latter free.

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.

When I shall be dead, the principles of which I am composed will still perform their part in the universe, and will be equally useful in the grand fabric, as when they composed this individual creature. The difference to the whole will be no greater betwixt my being in a chamber and in the open air. The one change is of more importance to me than the other; but not more so to the universe.

All morality depends upon our sentiments; and when any action or quality of the mind pleases us after a certain manner we say it is virtuous; and when the neglect or nonperformance of it displeases us after a like manner, we say that we lie under an obligation to perform it.