Stephen Hawking Quotes

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.

Science is prediction, not explanation.

It is a very long and very difficult road from a fact to a conclusion. But it is a million times longer from a theory to a fact.

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

Observation and theory get on best when they are mixed together, both helping one another in the pursuit of truth. It is a good rule not to put overmuch confidence in a theory until it has been confirmed by observation. I hope I shall not shock the experimental physicists too much if I add that it is also a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory.

A good hypothesis in science must have other properties than those of the phenomenon it is immediately invoked to explain, otherwise it is not prolific enough.

The hypotheses we accept ought to explain phenomena which we have observed. But they ought to do more than this: our hypotheses ought to foretell phenomena which have not yet been observed.

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

Theories are not rejected by cirsumstantial evidence: it takes a theory to beat a theory.

The theory must not contradict empirical facts.

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.

A theory has only the alternative of being right or wrong. A model has a third possibility: it may be right, but irrelevant.

The situation in the sciences is this: A concept or an idea which cannot be measured or cannot be referred directly to experiment may or may not be useful. It need not exist in a theory.

Thus, in general, in the first instance, the direction of interest in empirical fact will be canalised by the logical structure of the theoretical system.

That said, ID does not qualify as science because it gives us nothing to test or measure. Science requires replicable tests involving measurable variables.

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 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.

To me, what makes physics physics is that experiment is intimately connected to theory. It's one whole.

There is no justifiable prediction about how the hypothesis will hold up in the future; its degree of corroboration simply is a historical statement describing how severely the hypothesis has been tested in the past.

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 final test of a theory is its capacity to solve the problems which originated it.

A theory can be proved by experiment; but no path leads from experiment to the birth of a theory.

As you know, a theory in physics is not useful unless it is able to predict underlined effects which we would otherwise expect.