Karl Popper Quotes

In science, nothing is ever 100% proven.

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

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

I think that we shall have to get accustomed to the idea that we must not look upon science as a 'body of knowledge,' but rather as a system of hypotheses; that is to say, as a system of guesses or anticipations which in principle cannot be justified, but with which we work as long as they stand up to tests, and of which we are never justified in saying that we know they are 'true' or 'more or less certain' or even 'probable.'

Progress is achieved by exchanging our theories for new ones which go further than the old, until we find one based on a larger number of facts. ... Theories are only hypotheses, verified by more or less numerous facts. Those verified by the most facts are the best, but even then they are never final, never to be absolutely believed.

Science does not give us absolute and final certainty. It only gives us assurance within the limits of our mental abilities and the prevailing state of scientific thought.

Science makes no pretension to eternal truth or absolute truth.

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

Science makes no claim to infallibility; it leaves that claim to be made by theologians.

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

There is not a single truth of science upon which we ought to bet more than about a million of millions to one.

No scientist ever believes that he has the final answer or the ultimate truth on anything.

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

Theories without facts may be barren, but facts without theories are meaningless.

Not only are facts and theories in constant disharmony, they are never as neatly separated as everyone makes them out to be.

...As Thomas Kuhn pointed out in The Structure of Scientific Revolutions, new scientific theories in any field are regarded with skepticism because scientists become attached to the old perspective earlier in their careers.

The game of science is, in principle, without end. He who decides one day that scientific statements do not call for any further test, and that they can be regarded as finally verified, retires from the game.

Science is uncertain.

I’ve spent something like 17 years working on a theory for which there is essentially no direct experimental support.

Progress in science comes when experiments contradict theory.

In science , all conclusions are provisional, subject to new evidence and better arguments, the very antithesis of religious faith.

Science says the first word on everything, and the last word on nothing.

The only universal attribute of scientific statements resides in their potential fallibility. If a claim cannot be disproven, it does not belong to the enterprise of science.

It appears that anything you say about the way that theory and experiment may interact is likely to be correct, and anything you say about the way that theory and experiment must interact is likely to be wrong.

[T]he true natural sciences lock together in theory and evidence to form the ineradicable technical base of modern civilization. The pseudosciences satisfy personal psychological needs... but lack the ideas or the means to contribute to the technical base.