Karl Popper Quotes

Science is the acceptance of what works and the rejection of what does not. That needs more courage than we might think.

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.

In these researches I followed the principles of the experimental method that we have established, i.e., that, in presence of a well-noted, new fact which contradicts a theory, instead of keeping the theory and abandoning the fact, I should keep and study the fact, and I hastened to give up the theory.

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.

Our belief in any particular natural law cannot have a safer basis than our unsuccessful critical attempts to refute it.

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

In nature, when you conduct science, it is the natural world that is the ultimate decider in what is true and what is not.

If you're a physicist, for heaven's sake, and here is the experiment, and you have a theory, and the theory doesn't agree with the experiment, then you have to cut out the theory. You were wrong with the theory.

I cannot stress often enough that what science is all about is not proving things to be true but proving them to be false.

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.

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

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.

It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is if it disagrees with experiment it is wrong. That is all there is to it.

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 will be well-testable theories, hardly testable theories, and non-testable theories. Those which are non-testable are of no interest to empirical scientists. They may be described as metaphysical.

Science, at bottom, is really anti-intellectual. It always distrusts pure reason, and demands the production of objective fact.

It is a mistake to believe that science consists in nothing but conclusively proved propositions, and it is unjust to demand that it should. It is a demand made by those who feel a craving for authority in some form to replace the religious catechism by something else, even a scientific one.

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.

The scientific tradition is distinguished from the pre-scientific tradition by having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them.

First you guess. Don't laugh, this is the most important step. Then you compute the consequences. Compare the consequences to experience. If it disagrees with experience, the guess is wrong. In that simple statement is the key to science. It doesn't matter how beautiful your guess is or how smart you are or what your name is. If it disagrees with experience, it's wrong. That's all there is to it.

A single test which proves some piece of theory wrong is more valuable than a hundred tests showing that idea might be true.

If it disagrees with experiment, it's wrong.

I'm not a religious man... I find I am a fan of science. I believe in science. A humility before the facts. I find that a moving and beautiful thing. And belief in the unknown I find less interesting. I find the known and the knowable interesting enough.

The man of science dissects the statement, verifies the facts, and demonstrates connection even where he cannot its purpose.

When all is said and done, science actually takes hard work and a willingness to sometimes find out that your most cherished hypothesis is wrong.