„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

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„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.“
— Stephen Hawking
„I accumulated in those years so fine a surplus in the Book of Observance that I have been drawing confidently upon it ever since.“
— Winston S. Churchill
„Our celebration of initiative and enterprise, our insistence on hard work and personal responsibility, these are constants in our character. But we have always understood that when times change, so must we; that fidelity to our founding principles requires new responses to new challenges; that preserving our individual freedoms ultimately requires collective action.“
— Barack Obama