Negative Capability, that is when man is capable of being in uncertainties, Mysteries, doubts, without any irritable reaching after fact & reason—Coleridge, for instance, would let go by a fine isolated verisimilitude caught from the Penetralium of mystery, from being incapable of remaining content with half knowledge.

And for mathematical sciences, he that doubts their certainty hath need of a dose of Hellebore.

I long to speak out the intense inspiration that comes to me from the lives of strong women. They have made of their lives a great adventure.

I was there when Abbe Georges Lemaître first proposed this [Big Bang] theory. ... There is no rational reason to doubt that the universe has existed indefinitely, for an infinite time. .... It is only myth that attempts to say how the universe came to be, either four thousand or twenty billion years ago.
[Expressing his belief that the Big Bang is a myth devised to explain creation. He said he heard Lemaître (who was, at the time both a member of the Catholic hierarchy and an accomplished scientist) say in private that this theory was a way to reconcile science with St. Thomas Aquinas' theological dictum of creatio ex nihilo—creation out of nothing.]

If knowledge is my God, doubt would be my religion.

In science, self-satisfaction is death. Personal self-satisfaction is the death of the scientist. Collective self-satisfaction is the death of the research. It is restlessness, anxiety, dissatisfaction, agony of mind that nourish science.

It has sometimes been said that the success of the Origin proved 'that the subject was in the air,' or 'that men's minds were prepared for it.' I do not think that this is strictly true, for I occasionally sounded not a few naturalists, and never happened to come across a single one who seemed to doubt about the permanence of species.

It may be observed of mathematicians that they only meddle with such things as are certain, passing by those that are doubtful and unknown. They profess not to know all things, neither do they affect to speak of all things. What they know to be true, and can make good by invincible arguments, that they publish and insert among their theorems. Of other things they are silent and pass no judgment at all, chusing [choosing] rather to acknowledge their ignorance, than affirm anything rashly. They affirm nothing among their arguments or assertions which is not most manifestly known and examined with utmost rigour, rejecting all probable conjectures and little witticisms. They submit nothing to authority, indulge no affection, detest subterfuges of words, and declare their sentiments, as in a Court of Judicature [Justice], without passion, without apology; knowing that their reasons, as Seneca testifies of them, are not brought to persuade, but to compel.

One of the main causes of our artistic decline lies beyond doubt in the separation of art and science.

Scientific knowledge advances haltingly and is stimulated by contention and doubt.

The doubter is a true man of science: he doubts only himself and his interpretations, but he believes in science.

The first key to wisdom is assiduous and frequent questioning ... For by doubting we come to inquiry, and by inquiry we arrive at truth.

The great experimental principle, then, is doubt, that philosophic doubt which leaves to the mind its freedom and initiative, and from which the virtues most valuable to investigators in physiology and medicine are derived.

The mind God is looking for in man is a doubting, questioning mind, not a dogmatic mind; dogmatic reasoning is wrong reasoning. Dogmatic reason ties a huge rock to a man’s foot and stops him forever from advancing.

The power of the eye could not be extended further in the opened living animal, hence 1 had believed that this body of the blood breaks into the empty space, and is collected again by a gaping vessel and by the structure of the walls. The tortuous and diffused motion of the blood in divers directions, and its union at a determinate place offered a handle to this. But the dried lung of the frog made my belief dubious. This lung had, by chance, preserved the redness of the blood in (what afterwards proved to be) the smallest vessels, where by means of a more perfect lens, no more there met the eye the points forming the skin called Sagrino, but vessels mingled annularly. And, so great is the divarication of these vessels as they go out, here from a vein, there from an artery, that order is no longer preserved, but a network appears made . up of the prolongations of both vessels. This network occupies not only the whole floor, but extends also to the walls, and is attached to the outgoing vessel, as 1 could see with greater difficulty but more abundantly in the oblong lung of a tortoise, which is similarly membranous and transparent. Here it was clear to sense that the blood flows away through the tortuous vessels, that it is not poured into spaces but always works through tubules, and is dispersed by the multiplex winding of the vessels.

The skeptic does not mean him who doubts, but him who investigates or researches, as opposed to him who asserts and thinks that he has found. The one is the man who studies the problem and the other is the man who gives us a formula, correct or incorrect, as the solution of it.

The trouble with the world is that the stupid are cocksure and the intelligent full of doubt.

There are two ways to slide easily through life; to believe everything or to doubt everything. Both ways save us from thinking.

There is no permanence in doubt; it incites the mind to closer inquiry and experiment, from which, if rightly managed, certainty proceeds, and in this alone can man find thorough satisfaction.

There must be no barriers to freedom of inquiry. There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... Our political life is also predicated on openness. We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress.

To have doubted one's own first principles is the mark of a civilized man.

True science teaches, above all, to doubt and to be ignorant.

We do not doubt to assert, that air does not serve for the motion of the lungs, but rather to communicate something to the blood ... It is very likely that it is the fine nitrous particles, with which the air abounds, that are communicated to the blood through the lungs.

William James used to preach the 'will to believe'. For my part, I should wish to preach the 'will to doubt.' … What is wanted is not the will to believe, but the wish to find out, which is the exact opposite.

William James used to preach the 'will to believe.' For my part, I should wish to preach the 'will to doubt' ... what is wanted is not the will to believe, but the wish to find out, which is the exact opposite.

Without any doubt, the regularity which astronomy shows us in the movements of the comets takes place in all phenomena. The trajectory of a simple molecule of air or vapour is regulated in a manner as certain as that of the planetary orbits; the only difference between them is that which is contributed by our ignorance. Probability is relative in part to this ignorance, and in part to our knowledge.

[Magic] enables man to carry out with confidence his important tasks, to maintain his poise and his mental integrity in fits of anger, in the throes of hate, of unrequited love, of despair and anxiety. The function of magic is to ritualize man's optimism, to enhance his faith in the victory of hope over fear. Magic expresses the greater value for man of confidence over doubt, of steadfastness over vacillation, of optimism over pessimism.