A harmless and a buoyant cheerfulness are not infrequent concomitants of genius; and we are never more deceived than when we mistake gravity for greatness, solemnity for science, and pomposity for erudition.

Body and mind, like man and wife, do not always agree to die together.

Examinations are formidable even to the best prepared, for the greatest fool may ask more than the wisest man can answer.

He who gives a portion of his time and talent to the investigation of mathematical truth will come to all other questions with a decided advantage over his opponents. He will be in argument what the ancient Romans were in the field: to them the day of battle was a day of comparative recreation, because they were ever accustomed to exercise with arms much heavier than they fought; and reviews differed from a real battle in two respects: they encountered more fatigue, but the victory was bloodless.

Hypochondriacs squander large sums of time in search of nostrums by which they vainly hope they may get more time to squander.

If any woman were to hang a man for stealing her picture, although it were set in gold, it would be a new case in law; but, if he carried off the setting, and left the portrait, I would not answer for his safety.

In physics, there are many discoveries already made, too powerful to be safe, too unmanageable to be subservient.

In science, reason is the guide; in poetry, taste. The object of the one is truth, which is uniform and indivisible; the object of the other is beauty, which is multiform and varied.

It is almost as difficult to make a man unlearn his errors, as his knowledge. Mal-information is more hopeless than non-information: for error is always more busy than ignorance. Ignorance is a blank sheet on which we may write; but error is a scribbled one on which we first erase. Ignorance is contented to stand still with her back to the truth; but error is more presumptuous, and proceeds, in the same direction. Ignorance has no light, but error follows a false one. The consequence is, that error, when she retraces her footsteps, has farther to go, before we can arrive at the truth, than ignorance.

It is bad when the mind survives the body; and worse still when the body survives the mind; but, when both these survive our spirits, our hopes, and our health, this is worst of all.

It is better to have recourse to a Quack, if he can cure our disorder, although he cannot explain it than to a Physician, if he can explain our disease but cannot cure it.

It is not so difficult a task as to plant new truths, as to root out old errors

Let any man reflect on the revolution produced in society by two simple and common things, glass and gunpowder.

Literature has her quacks no less than medicine, and they are divided into two classes; those who have erudition without genius, and those who have volubility, without depth; we shall get second-hand sense from the one, and original nonsense from the other.

Metaphor … may be said to be the algebra of language.

Most females will forgive a liberty, rather than a slight.

No disorders have employed so many quacks, as those that have no cure; and no sciences have exercised so many quills, as those that have no certainty.

Professors in every branch of the sciences, prefer their own theories to truth: the reason is that their theories are private property, but truth is common stock.

That which is perfect in science, is most commonly the elaborate result of successive improvements, and of various judgments exercised in the rejection of what was wrong, no less than in the adoption of what was right.

The acquirements of science may be termed the armour of the mind; but that armour would be worse than useless, that cost us all we had, and left us nothing to defend.

The Chinese, who aspire to be thought an enlightened nation, to this day are ignorant of the circulation of the blood; and even in England the man who made that noble discovery lost all his practice in the consequence of his ingenuity; and Hume informs us that no physician in the United Kingdom who had attained the age of forty ever submitted to become a convert to Harvey’s theory, but went on preferring numpsimus to sumpsimus to the day of his death.

The poorest man would not part with health for money, but … the richest would gladly part with all their money for health.

The rich man, gasping for breath … feels at last the impotence of gold; that death which he dreaded at a distance as an enemy, he now hails when he is near, as a friend; a friend that alone can bring the peace his treasures cannot purchase, and remove the pain his physicians cannot cure.

The science of legislation, is like that of medicine; in one respect, that it is far more easy to point out what will do harm, than what will do good.

The science of mathematics performs more than it promises, but the science of metaphysics promises more than it performs.

The science of mathematics performs more than it promises…. The study of the mathematics, like the Nile, begins in minuteness, but ends in magnificence.

The science of metaphysics promises more than it performs. The study of … metaphysics begins with a torrent of tropes, and a copious current of words, yet loses itself at last, in obscurity and conjecture, like the Niger in his barren deserts of sand.

We … are profiting not only by the knowledge, but also by the ignorance, not only by the discoveries, but also by the errors of our forefathers; for the march of science, like that of time, has been progressing in the darkness, no less than in the light.