Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.

Obscurity, indeed, is painful to the mind as well as to the eye; but to bring light from obscurity, by whatever labour, must needsbe delightful and rejoicing.

There is nothing, in itself, valuable or despicable, desirable or hateful, beautiful or deformed; but that these attributes arise from the particular constitution and fabric of human sentiment and affection.

Accuracy is, in every case, advantageous to beauty, and just reasoning to delicate sentiment. In vain would we exalt the one by depreciating the other.

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.

Superstition is an enemy to civil liberty.

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.