Karl Popper Quotes

In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.

The criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.

Science does not limit itself merely to what is currently verifiable. But it is interested in questions that are potentially verifiable (or, rather, falsifiable).

Falsifiability for a theory is great, but a theory can still be respectable even if it is not falsifiable, as long as it is verifiable.

A good scientific theory is one which is falsifiable, which has not been falsified.

It is easy to obtain confirmations, or verifications, for nearly every theory-if we look for confirmations. Confirmations should count only if they are the result of risky predictions... A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice. Every genuine test of a theory is an attempt to falsify it, or refute it.

A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.

It is certainly not the least charm of a theory that it is refutable.

Science is different to all other systems of thought because you dont need faith in it, you can check that it works.

Everything that people say is testable.

No amount of experimentation can ever prove me right; a single experiment can prove me wrong.

Science is constantly proved all the time. If we take something like any fiction, any holy book, and destroyed it, in a thousand years' time, that wouldn't come back just as it was. Whereas if we took every science book and every fact and destroyed them all, in a thousand years they'd all be back because all the same tests would be the same result.

In science, if an idea is not falsifiable, it is not that it is wrong, it is that we cannot determine if it is wrong, and thus it is not even wrong.

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.

The strength of a theory is not what it allows, but what it prohibits; if you can invent an equally persuasive explanation for any outcome, you have zero knowledge.

There can be no ultimate statements science: there can be no statements in science which can not be tested, and therefore none which cannot in principle be refuted, by falsifying some of the conclusions which can be deduced from them.

It must be possible for an empirical system to be refuted by experience.

Maybe scientists are fundamentalist when it comes to defining in some abstract way what is meant by 'truth'. But so is everybody else. I am no more fundamentalist when I say evolution is true than when I say it is true that New Zealand is in the southern hemisphere. We believe in evolution because the evidence supports it, and we would abandon it overnight if new evidence arose to disprove it.

(Crank theories) always violated the first rule of a scientific model: they were uncheckable.

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.

The problem with intelligent-design theory, is not that it is false but that it is not falsifiable. Not being susceptible to contradicting evidence, it is not a testable hypothesis. Hence it is not a scientific but a creedal tenet - a matter of faith, unsuited to a public school's science curriculum.

Every genuine test of a theory is an attempt to falsify it, or to refute it.

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.

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

Evolution is not a fact. Evolution doesn't even qualify as a theory or as a hypothesis. It is a metaphysical research program, and it is not really testable science.