No theory is good unless it permits, not rest, but the greatest work. No theory is good except on condition that one use it to go on beyond.
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Detached Pages, entry for 1913Andre Gide
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. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.
Stephen Hawking
Jesus never said anything about absurdity, and he never indicated for one flash of time that he was aware of the preposterousness of his theory about himself. And he didn't even try to make the theory understandable in terms of the reality and experience of the rest of us. For if everybody else is also not what Jesus said he was, what good is what he said?
William Saroyan
Third Theory.—According to this theory, there is nothing in the whole Universe... that is due to chance; everything is the result of will, intention, and rule. It is a matter of course that he who rules must know. The Mohametan Ashariyah adhere to this theory, notwithstanding evident absurdities implied in it. ...The Ashariyah were therefore compelled to assume that motion and rest of living beings are predestined, and that it is not in the power of a man to do a certain thing or to leave it undone. ...It follows also from this theory, that precepts are perfectly useless, since the people to whom any law is given... can neither do what they are commanded nor abstain from what they are forbidden. ...According to this theory, it must also be assumed that the actions of God have no final cause. All these absurdities are admitted by the Ashariyah for the purpose of saving this theory.
Maimonides
The Steady State theory was what Karl Popper would call a good scientific theory: it made definite predictions, which could be tested by observation, and possibly falsified. Unfortunately for the theory, they were falsified.
Stephen Hawking
A theory is only as good as its assumptions. If the premises are false, the theory has no real scientific value. The only scientific criterion for judging the validity of a scientific theory is a confrontation with the data of experience.
Maurice Allais
Gide, Andre
Gielgud, John
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