Dubitanda quippe ad inquisitionem venimus; inquirendo veritatem percipimus. (By doubting we come to enquiry, and through enquiry we perceive truth.)

A mind which has once imbibed a taste for scientific enquiry, and has learnt the habit of applying its principles readily to the cases which occur, has within itself an inexhaustible source of pure and exciting contemplations.

A scientist strives to understand the work of Nature. But with our insufficient talents as scientists, we do not hit upon the truth all at once. We must content ourselves with tracking it down, enveloped in considerable darkness, which leads us to make new mistakes and errors. By diligent examination, we may at length little by little peel off the thickest layers, but we seldom get the core quite free, so that finally we have to be satisfied with a little incomplete knowledge.

All the world is a laboratory to the inquiring mind.

Be less curious about people and more curious about ideas.

By far the most important consequence of the conceptual revolution brought about in physics by relativity and quantum theory lies not in such details as that meter sticks shorten when they move or that simultaneous position and momentum have no meaning, but in the insight that we had not been using our minds properly and that it is important to find out how to do so.

Development of Western science is based on two great achievements: the invention of the formal logical system (in Euclidean geometry) by the Greek philosophers, and the discovery of the possibility to find out causal relationships by systematic experiment (during the Renaissance).

Far from becoming discouraged, the philosopher should applaud nature, even when she appears miserly of herself or overly mysterious, and should feel pleased that as he lifts one part of her veil, she allows him to glimpse an immense number of other objects, all worthy of investigation. For what we already know should allow us to judge of what we will be able to know; the human mind has no frontiers, it extends proportionately as the universe displays itself; man, then, can and must attempt all, and he needs only time in order to know all. By multiplying his observations, he could even see and foresee all phenomena, all of nature's occurrences, with as much truth and certainty as if he were deducing them directly from causes. And what more excusable or even more noble enthusiasm could there be than that of believing man capable of recognizing all the powers, and discovering through his investigations all the secrets, of nature!

For you teach very clearly by your behaviour how slowly and how meagerly our senses proceed in the investigation of ever inexhaustible nature.

I think that considerable progress can be made in the analysis of the operations of nature by the scholar who reduces rather complicated phenomena to their proximate causes and primitive forces, even though the causes of those causes have not yet been detected.

If a specific question has meaning, it must be possible to find operations by which an answer may be given to it ... I believe that many of the questions asked about social and philosophical subjects will be found to be meaningless when examined from the point of view of operations.

If the human race ever stops acting on the basis of what it thinks it knows, paralyzed by fear that its knowledge may be wrong, then Homo sapiens will be making its application for membership in the dinosaur club.

If you walk along the street you will encounter a number of scientific problems. Of these, about 80 per cent are insoluble, while 19½ per cent are trivial. There is then perhaps half a per cent where skill, persistence, courage, creativity and originality can make a difference. It is always the task of the academic to swim in that half a per cent, asking the questions through which some progress can be made.

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 is the business of science to offer rational explanations for all the events in the real world, and any scientist who calls on God to explain something is falling down on his job. This applies as much to the start of the expansion as to any other event. If the explanation is not forthcoming at once, the scientist must suspend judgment: but if he is worth his salt he will always maintain that a rational explanation will eventually be found. This is the one piece of dogmatism that a scientist can allow himself—and without it science would be in danger of giving way to superstition every time that a problem defied solution for a few years.

It was a great step in science when men became convinced that, in order to understand the nature of things, they must begin by asking, not whether a thing is good or bad, noxious or beneficial, but of what kind it is? And how much is there of it? Quality and Quantity were then first recognised as the primary features to be observed in scientific inquiry.

Man is not born to solve the problem of the universe, but to find out where the problem begins and then restrain himself within the limits of the comprehensible.

People have noted with admiration how the progress of scientific enquiry is like the growth of a coral reef; each generation of little toilers building a sure foundation on which their successors may build yet further. The simile is apt in many ways, and in one way in particular that is worth considering. When we see how industrious and how prolific are the coral insects, our chief astonishment should be, not how vast are the structures they have built, but how few and scattered. Why is not every coast lined with coral? Why is the abyss if ocean not bridged with it. The answer is that coral only lives under certain limitations; it can only thrive at certain depths, in water of certain temperatures and salinities; outside these limits it languishes and dies. Science is like coral in this. Scientific investigators can only work in certain spots of the ocean of Being, where they are at home, and all outside is unknown to them...

Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. In our endeavour to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hears its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all the things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism and he cannot even imagine the possibility or the meaning of such a comparison. But he certainly believes that, as his knowledge increases, his picture of reality will become simpler and simpler and will explain a wider and wider range of his sensuous impressions. He may also believe in the existence of the ideal limit of knowledge and that it is approached by the human mind. He may call this ideal limit the objective truth.

Reason and free inquiry are the only effectual agents against error.

Religious creeds are a great obstacle to any full sympathy between the outlook of the scientist and the outlook which religion is so often supposed to require ... The spirit of seeking which animates us refuses to regard any kind of creed as its goal. It would be a shock to come across a university where it was the practice of the students to recite adherence to Newton's laws of motion, to Maxwell's equations and to the electromagnetic theory of light. We should not deplore it the less if our own pet theory happened to be included, or if the list were brought up to date every few years. We should say that the students cannot possibly realise the intention of scientific training if they are taught to look on these results as things to be recited and subscribed to. Science may fall short of its ideal, and although the peril scarcely takes this extreme form, it is not always easy, particularly in popular science, to maintain our stand against creed and dogma.

Science is the attempt to make the chaotic diversity of our sense- experience correspond to a logically uniform system of thought.

Science is wonderful at destroying metaphysical answers, but incapable of providing substitute ones. Science takes away foundations without providing a replacement. Whether we want to be there or not, science has put us in the position of having to live without foundations. It was shocking when Nietzsche said this, but today it is commonplace; our historical position- and no end to it is in sight-is that of having to philosophise without 'foundations'.

Science teaches us, in effect, to submit our reason to the truth and to know and judge of things as they are—that is to say, as they themselves choose to be and not as we would have them to be.

Sometimes I am a little unkind to all my many friends in education ... by saying that from the time it learns to talk every child makes a dreadful nuisance of itself by asking 'Why?'. To stop this nuisance society has invented a marvellous system called education which, for the majority of people, brings to an end their desire to ask that question. The few failures of this system are known as scientists.

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 human understanding is unquiet; it cannot stop or rest, and still presses onward, but in vain. Therefore it is that we cannot conceive of any end or limit to the world, but always as of necessity it occurs to us that there is something beyond... But he is no less an unskilled and shallow philosopher who seeks causes of that which is most general, than he who in things subordinate and subaltern omits to do so

The most erroneous stories are those we think we know best—and therefore never scrutinize or question.

The text-book is rare that stimulates its reader to ask, Why is this so? Or, How does this connect with what has been read elsewhere?

The traditional disputes of philosophers are, for the most part, as unwarranted as they are unfruitful. The surest way to end them is to establish beyond question what should be the purpose and method of a philosophical enquiry. And this is by no means so difficult a task as the history of philosophy would lead one to suppose. For if there are any questions which science leaves it to philosophy to answer, a straightforward process of elimination must lead to their discovery.

To him [Faraday], as to all true philosophers, the main value of a fact was its position and suggestiveness in the general sequence of scientific truth.

We call that fire of the black thunder-cloud 'electricity,' and lecture learnedly about it, and grind the like of it out of glass and silk: but what is it? What made it? Whence comes it? Whither goes it?

We know next to nothing about virtually everything. It is not necessary to know the origin of the universe; it is necessary to want to know. Civilization depends not on any particular knowledge, but on the disposition to crave knowledge

When we think how narrow and devious this path of nature is, how dimly we can trace it, for all our lamps of science, and how from the darkness which girds it round great and terrible possibilities loom ever shadowly upwards, it is a bold and a confident man who will put a limit to the strange by-oaths into which the human spirit may wander.

While it is true that scientific results are entirely independent from religious and moral considerations, those individuals to whom we owe the great creative achievements of science were all of them imbued with the truly religious conviction that this universe of ours is something perfect and susceptible to the rational striving for knowledge. If this conviction had not been a strongly emotional one and if those searching for knowledge had not been inspired by Spinoza's Amor Dei Intellectualis, they would hardly have been capable of that untiring devotion which alone enables man to attain his greatest achievements.

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.

Yet is it possible in terms of the motion of atoms to explain how men can invent an electric motor, or design and build a great cathedral? If such achievements represent anything more than the requirements of physical law, it means that science must investigate the additional controlling factors, whatever they may be, in order that the world of nature may be adequately understood. For a science which describes only the motions of inanimate things but fails to include the actions of living organisms cannot claim universality.

[John] Dalton was a man of regular habits. For fifty-seven years he walked out of Manchester every day; he measured the rainfall, the temperature—a singularly monotonous enterprise in this climate. Of all that mass of data, nothing whatever came. But of the one searching, almost childlike question about the weights that enter the construction of these simple molecules—out of that came modern atomic theory. That is the essence of science: ask an impertinent question, and you are on the way to the pertinent answer.