Karl Popper Quotes

'Incontrovertible' is not a scientific word. Nothing is incontrovertible in science.

What scientists believe today may have to be revised in the light of observations made tomorrow, [In that sense] we can describe all our science as "theory.

The truth of a theory can never be proven, for one never knows if future experience will contradict its conclusions.

What is believed to be a fact is only a fact until another fact supersedes it. Science is only a fashion. Nothing more.

The more experiences and experiments accumulate in the exploration of nature, the more precarious the theories become. But it is not always good to discard them immediately on this account. For every hypothesis which once was sound was useful for thinking of previous phenomena in the proper interrelations and for keeping them in context. We ought to set down contradictory experiences separately, until enough have accumulated to make building a new structure worthwhile.

There never comes a point where a theory can be said to be true. The most that one can claim for any theory is that it has shared the successes of all its rivals and that it has passed at least one test which they have failed.

In science, there are no universal truths, just views of the world that have yet to be shown to be false.

In science, 'fact' can only mean 'confirmed to such a degree that it would be perverse to withhold provisional assent.' I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.

Science has authority, not because of white coats, or titles, but because of precision and transparency: you explain your theory, set out your evidence, and reference the studies that support your case.

We don't regard any scientific theory as the absolute truth.

In science, nothing is ever 100% proven.

I hold that the propositions embodied in natural science are not derived by any definite rule from the data of experience, and that they can neither be verified nor falsified by experience according to any definite rule.

Now obviously the propositions of the system have reference to matters of empirical fact; if they did not, they could have no claim to be called scientific.

In the absence of absolute knowledge one theory is as good as another, as long as it meets all the requirements of practical tests. My theory may be upset tomorrow, but today I look at it as the best of all.

Scientists don't read theology; they don't read philosophy. It doesn't make any difference to what they're doing - for better or worse, it may not be a value judgment, but it's true.

It is generally believed that our science is empirical and that we draw our concepts and our mathematical constructs from the empirical data. If this were the whole truth, we should, when entering into a new field, introduce only such quantities as can directly be observed, and formulate natural laws only by means of these quantities.

Science is composed of laws which were originally based on a small, carefully selected set of observations, often not very accurately measured originally; but the laws have later been found to apply over much wider ranges of observations and much more accurately than the original data justified.

The faith of scientists in the power and truth of mathematics is so implicit that their work has gradually become less and less observation, and more and more calculation.... But the facts which are accepted by virtue of these tests are not actually observed at all.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory.

Nor must we forget that in science there are no final truths.

Science is at no moment quite right, but it is seldom quite wrong, and has, as a rule, a better chance of being right than the theories of the unscientific. It is, therefore, rational to accept it hypothetically.

Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.

Science is not the affirmation of a set of beliefs but a process of inquiry aimed at building a testable body of knowledge constantly open to rejection or confirmation. In science, knowledge is fluid and certainty fleeting. That is at the heart of its limitations. It is also its greatest strength.

Almost everyone... seems to be quite sure that the differences between the methodologies of history and of the natural sciences are vast. For, we are assured, it is well known that in the natural sciences we start from observation and proceed by induction to theory. And is it not obvious that in history we proceed very differently? Yes, I agree that we proceed very differently. But we do so in the natural sciences as well.

Science is not 'organized common sense'; at its most exciting, it reformulates our view of the world by imposing powerful theories against the ancient, anthropocentric prejudices that we call intuition.