Alfred Jules Ayer Quotes

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

If it disagrees with experiment, it's wrong.

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.

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.

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.

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

The ultimate arbiter of truth is experiment, not the comfort one derives from one's a priori beliefs, nor the beauty or elegance one ascribes to one's theoretical models.

The theory must not contradict empirical facts.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it.

Whenever a true theory appears, it will be its own evidence. Its test is, that it will explain all phenomena.

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

A valid scientific theory is predictive, verifiable, and replicable. To me, that's beautiful.

It is an acknowledged truth in philosophy that a just theory will always be confirmed by experiment.

If the facts are contrary to any predictions, then the hypothesis is wrong no matter how appealing.

Where we have good, testable explanations, they then have to be tested, and we drop the ones that fail the tests.

If the experiments which I urge be defective, it cannot be difficult to show the defects; but if valid, then by proving the theory, they must render all objections invalid.

It is also a good rule not to put overmuch confidence in the observational results that are put forward until they are confirmed by theory.

It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.

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.

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

To say that prediction is the purpose of a scientific theory is to confuse means with ends. It is like saying that the purpose of a spaceship is to burn fuel. ... Passing experimental tests is only one of many things a theory has to do to achieve the real purpose of science, which is to explain the world.

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

The facts will eventually test all our theories, and they form, after all, the only impartial jury to which we can appeal.

In degenerating programmes, however, theories are fabricated only in order to accommodate known facts

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.