Among the many inconsistencies which folly produces or infirmity suffers in the human mind, there has often been observed a manifest and striking contrariety between the life of an author and his writings... Those whom the appearance of virtue or the evidence of genius has tempted to a nearer knowledge of the writer, in whose performances they may be found, have indeed had frequent reason to repent their curiosity.

You never find people laboring to convince you that you may live very happily upon a plentiful income.

Every man's affairs, however little, are important to himself.

Novelty is indeed necessary to preserve eagerness and alacrity; but art and nature have stores inexhaustible by human intellects, and every moment produces something new to him who has quickened his faculties by diligent observation.

There is in this world no real delight (excepting those of sensuality), but exchange of ideas in conversation.

I inherited a vile melancholy from my father, which has made me mad all my life, at least not sober.

The mathematicians are well acquainted with the difference between pure science, which has only to do with ideas, and the application of its laws to the use of life, in which they are constrained to submit to the imperfections of matter and the influence of accidents.