The scientific imagination always restrains itself within the limits of probability.

Learn what is true in order to do what is right.

The child who has been taught to make an accurate elevation, plan, and section of a pint pot has had an admirable training in accuracy of eye and hand.

There is no sea more dangerous than the ocean of practical politics none in which there is more need of good pilotage and of a single, unfaltering purpose when the waves rise high.

Science commits suicide when it adopts a creed.

The scientific spirit is of more value than its products, and irrationally held truths may be more harmful than reasoned errors.

The improver of natural knowledge absolutely refuses to acknowledge authority, as such. For him, skepticism is the highest of duties; blind faith the one unpardonable sin.

Every great advance in natural knowledge has involved the absolute rejection of authority.

The great tragedy of science – the slaying of a beautiful hypothesis by an ugly fact.

The more rapidly truth is spread among mankind the better it will be for them. Only let us be sure that it is the truth.

Freedom and order are not incompatible… truth is strength… free discussion is the very life of truth.

Science has fulfilled her function when she has ascertained and enunciated truth.

It is not to be forgotten that what we call rational grounds for our beliefs are often extremely irrational attempts to justify our instincts.

There is but one right, and the possibilities of wrong are infinite.

Patience and tenacity are worth more than twice their weight of cleverness.

If a little knowledge is dangerous, where is the man who has so much as to be out of danger?

The man of science has learned to believe in justification, not by faith, but by verification.

Of moral purpose I see no trace in Nature. That is an article of exclusively human manufacture and very much to our credit.

The scientific imagination always restrains itself within the limits of probability.

Economy does not lie in sparing money, but in spending it wisely.

If a man cannot do brain work without stimulants of any kind, he had better turn to hand work it is an indication on Nature’s part that she did not mean him to be a head worker.

Science is organized common sense where many a beautiful theory was killed by an ugly fact.

Teach a child what is wise, that is morality. Teach him what is wise and beautiful, that is religion!

I protest that if some great Power would agree to make me always think what is true and do what is right, on condition of being turned into a sort of clock and would up every morning before I got out of bed, I should instantly close with the offer.

My experience of the world is that things left to themselves don’t get right.

In science, as in art, and, as I believe, in every other sphere of human activity, there may be wisdom in a multitude of counsellors, but it is only in one or two of them.

I do not say think as I think, but think in my way. Fear no shadows, least of all in that great spectre of personal unhappiness which binds half the world to orthodoxy.

Surely there is a time to submit to guidance and a time to take one’s own way at all hazards.

Proclaim human equality as loudly as you like, Witless will serve his brother.

I took thought, and invented what I conceived to be the appropriate title of ‘agnostic’.

Size is not grandeur, and territory does not make a nation.

Ecclesiasticism in science is only unfaithfulness to truth.

Science reckons many prophets, but there is not even a promise of a Messiah.

The great thing in the world is not so much to seek happiness as to earn peace and self-respect.

History warns us that it is the customary fate of new truths to begin as heresies and to end as superstitions.

The rung of a ladder was never meant to rest upon, but only to hold a man’s foot long enough to enable him to put the other somewhat higher.

Irrationally held truths may be more harmful than reasoned errors.

Misery is a match that never goes out.

Make up your mind to act decidedly and take the consequences. No good is ever done in this world by hesitation.

The results of political changes are hardly ever those which their friends hope or their foes fear.

The only question which any wise man can ask himself, and which any honest man will ask himself, is whether a doctrine is true or false.

There is the greatest practical benefit in making a few failures early in life.

Books are the money of Literature, but only the counters of Science.

Sit down before fact as a little child, be prepared to give up every conceived notion, follow humbly wherever and whatever abysses nature leads, or you will learn nothing.

I am content with nothing, restless and ambitious… and I despise myself for the vanity, which formed half the stimulus to my exertions. Oh would that I were one of those plodding wise fools who having once set their hand to the plough go on nothing doubting.

Logical consequences are the scarecrows of fools and the beacons of wise men.

My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.

The only freedom I care about is the freedom to do right; the freedom to do wrong I am ready to part with on the cheapest terms to anyone who will take it of me.

The chess-board is the world, the pieces are the phenomena of the universe, the rules of the game are what we call the laws of Nature. The player on the other side is hidden from us.

It is because the body is a machine that education is possible. Education is the formation of habits, a superinducing of an artificial organization upon the natural organization of the body.

In scientific work, those who refuse to go beyond fact rarely get as far as fact.

The ultimate court of appeal is observation and experiment… not authority.

The medieval university looked backwards; it professed to be a storehouse of old knowledge. The modern university looks forward, and is a factory of new knowledge.

The best men of the best epochs are simply those who make the fewest blunders and commit the fewest sins.

All truth, in the long run, is only common sense clarified.

I take it that the good of mankind means the attainment, by every man, of all the happiness which he can enjoy without diminishing the happiness of his fellow men.

I believe that history might be, and ought to be, taught in a new fashion so as to make the meaning of it as a process of evolution intelligible to the young.

It is the customary fate of new truths, to begin as heresies, and to end as superstitions.

Science is simply common sense at its best, that is, rigidly accurate in observation, and merciless to fallacy in logic.

Science and literature are not two things, but two sides of one thing.

Try to learn something about everything and everything about something.

Nothing can be more incorrect than the assumption one sometimes meets with, that physics has one method, chemistry another, and biology a third.

The only medicine for suffering, crime, and all other woes of mankind, is wisdom. Teach a man to read and write, and you have put into his hands the great keys of the wisdom box. But it is quite another thing to open the box.

It is one of the most saddening things in life that, try as we may, we can never be certain of making people happy, whereas we can almost always be certain of making them unhappy.

Science is nothing, but trained and organized common sense.

The doctrine that all men are, in any sense, or have been, at any time, free and equal, is an utterly baseless fiction.

The most considerable difference I note among men is not in their readiness to fall into error, but in their readiness to acknowledge these inevitable lapses.

The world is neither wise nor just, but it makes up for all its folly and injustice by being damnably sentimental.

It is not who is right, but what is right, that is of importance.

Time, whose tooth gnaws away everything else, is powerless against truth.

No delusion is greater than the notion that method and industry can make up for lack of mother-wit, either in science or in practical life.

No slavery can be abolished without a double emancipation, and the master will benefit by freedom more than the freed-man.

The struggle for existence holds as much in the intellectual as in the physical world. A theory is a species of thinking, and its right to exist is coextensive with its power of resisting extinction by its rivals.

The Bible has been the Magna Carta of the poor and of the oppressed.