„We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation.“

—  Richard Feynman, livre The Character of Physical Law

Source: The Character of Physical Law (1965), chapter 2, “ The Relation of Mathematics to Physics http://www.youtube.com/watch?v=M9ZYEb0Vf8U” referring to the law of conservation of angular momentum
Contexte: Now we have a problem. We can deduce, often, from one part of physics like the law of gravitation, a principle which turns out to be much more valid than the derivation. This doesn't happen in mathematics, that the theorems come out in places where they're not supposed to be!

Dernière mise à jour 4 juin 2020. L'histoire
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Richard Feynman4
physicien américain 1918 - 1988

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Abraham Lincoln photo

„But the proclamation, as law, either is valid, or is not valid. If it is not valid, it needs no retraction. If it is valid, it can not be retracted, any more than the dead can be brought to life.“

—  Abraham Lincoln 16th President of the United States 1809 - 1865

1860s, Letter to James C. Conkling (1863)
Contexte: But the proclamation, as law, either is valid, or is not valid. If it is not valid, it needs no retraction. If it is valid, it can not be retracted, any more than the dead can be brought to life. Some of you profess to think its retraction would operate favorably for the Union. Why better after the retraction, than before the issue? There was more than a year and a half of trial to suppress the rebellion before the proclamation issued, the last one hundred days of which passed under an explicit notice that it was coming, unless averted by those in revolt, returning to their allegiance. The war has certainly progressed as favorably for us, since the issue of the proclamation as before. I know as fully as one can know the opinions of others, that some of the commanders of our armies in the field who have given us our most important successes, believe the emancipation policy, and the use of colored troops, constitute the heaviest blow yet dealt to the rebellion; and that, at least one of those important successes, could not have been achieved when it was, but for the aid of black soldiers. Among the commanders holding these views are some who have never had any affinity with what is called abolitionism, or with republican party politics; but who hold them purely as military opinions. I submit these opinions as being entitled to some weight against the objections, often urged, that emancipation, and arming the blacks, are unwise as military measures, and were not adopted, as such, in good faith.

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„No human laws are of any validity if contrary to the law of nature; and such of them as are valid derive all their force and all their authority mediately or immediately from this original.“

—  Herbert Spencer, livre Social Statics

Thus writes Blackstone, to whom let all honour be given for having so far outseen the ideas of his time; and, indeed, we may say of our time. A good antidote, this, for those political superstitions which so widely prevail. A good check upon that sentiment of power-worship which still misleads us by magnifying the prerogatives of constitutional governments as it once did those of monarchs. Let men learn that a legislature is not “our God upon earth,” though, by the authority they ascribe to it, and the things they expect from it, they would seem to think it is. Let them learn rather that it is an institution serving a purely temporary purpose, whose power, when not stolen, is at the best borrowed.
Pt. III, Ch. 19 : The Right to Ignore the State, § 2
Social Statics (1851)

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William John Macquorn Rankine photo

„A physical theory, like an abstract science, consists of definitions and axioms as first principles, and of propositions, their consequences; but with these differences:—first, That in an abstract science, a definition assigns a name to a class of notions derived originally from observation, but not necessarily corresponding to any existing objects of real phenomena, and an axiom states a mutual relation amongst such notions, or the names denoting them; while in a physical science, a definition states properties common to a class of existing objects, or real phenomena, and a physical axiom states a general law as to the relations of phenomena; and, secondly,—That in an abstract science, the propositions first discovered are the most simple; whilst in a physical theory, the propositions first discovered are in general numerous and complex, being formal laws, the immediate results of observation and experiment, from which the definitions and axioms are subsequently arrived at by a process of reasoning differing from that whereby one proposition is deduced from another in an abstract science, partly in being more complex and difficult, and partly in being to a certain extent tentative, that is to say, involving the trial of conjectural principles, and their acceptance or rejection according as their consequences are found to agree or disagree with the formal laws deduced immediately from observation and experiment.“

—  William John Macquorn Rankine civil engineer 1820 - 1872

Source: "Outlines of the Science of Energetics," (1855), p. 121; Second paragraph

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„The laws of conscience, which we pretend to be derived from nature, proceed from custom.“

—  Michel De Montaigne, livre Essais

Book I, Ch. 22. Of Custom
Essais (1595), Bartlett's Familiar Quotations, 10th ed. (1919)

„He had doubted the correctness of the law of refraction of light but when he found in 1661 that he could deduce it from his Principle, he not only resolved his doubts about the law but felt all the more certain that his Principle was correct.“

—  Morris Kline American mathematician 1908 - 1992

Source: Mathematical Thought from Ancient to Modern Times (1972), p. 580
Contexte: Fermat knew that under reflection light takes the path requiring least time and, convinced that nature does indeed act simply and economically, affirmed in letters of 1657 and 1662 his Principle of Least Time, which states that light always takes the path requiring least time. He had doubted the correctness of the law of refraction of light but when he found in 1661 that he could deduce it from his Principle, he not only resolved his doubts about the law but felt all the more certain that his Principle was correct.... Huygens, who had at first objected to Fermat's Principle, showed that it does hold for the propagation of light in media with variable indices of refraction. Even Newton's first law of motion, which states that the straight line or shortest distance is the natural motion of a body, showed nature's desire to economize. These examples suggested that there might be a more general principle. The search for such a principle was undertaken by Maupertuis.

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„p>If justice be not a natural principle, it is no principle at all. If it be not a natural principle, there is no such thing as justice. If it be not a natural principle, all that men have ever said or written about it, from time immemorial, has been said and written about that which had no existence. If it be not a natural principle, all the appeals for justice that have ever been heard, and all the struggles for justice that have ever been witnessed, have been appeals and struggles for a mere fantasy, a vagary of the imagination, and not for a reality.If justice be not a natural principle, then there is no such thing as injustice; and all the crimes of which the world has been the scene, have been no crimes at all; but only simple events, like the falling of the rain, or the setting of the sun; events of which the victims had no more reason to complain than they had to complain of the running of the streams, or the growth of vegetation.If justice be not a natural principle, governments (so-called) have no more right or reason to take cognizance of it, or to pretend or profess to take cognizance of it, than they have to take cognizance, or to pretend or profess to take cognizance, of any other nonentity; and all their professions of establishing justice, or of maintaining justice, or of rewarding justice, are simply the mere gibberish of fools, or the frauds of imposters.But if justice be a natural principle, then it is necessarily an immutable one; and can no more be changed—by any power inferior to that which established it—than can the law of gravitation, the laws of light, the principles of mathematics, or any other natural law or principle whatever; and all attempts or assumptions, on the part of any man or body of men—whether calling themselves governments, or by any other name—to set up their own commands, wills, pleasure, or discretion, in the place of justice, as a rule of conduct for any human being, are as much an absurdity, an usurpation, and a tyranny, as would be their attempts to set up their own commands, wills, pleasure, or discretion in the place of any and all the physical, mental, and moral laws of the universe.If there be any such principle as justice, it is, of necessity, a natural principle; and, as such, it is a matter of science, to be learned and applied like any other science. And to talk of either adding to, or taking from, it, by legislation, is just as false, absurd, and ridiculous as it would be to talk of adding to, or taking from, mathematics, chemistry, or any other science, by legislation.</p“

—  Lysander Spooner Anarchist, Entrepreneur, Abolitionist 1808 - 1887

Sections I&#8211;II, p. 11&#8211;12
Natural Law; or The Science of Justice (1882), Chapter II. The Science of Justice (Continued)

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Martin Luther King, Jr. photo

„I want to deal with one or two of these mighty precious values that we've left behind, that if we're to go forward and to make this a better world, we must rediscover. The first is this—the first principle of value that we need to rediscover is this: that all reality hinges on moral foundations. In other words, that this is a moral universe, and that there are moral laws of the universe just as abiding as the physical laws. I'm not so sure we all believe that. We never doubt that there are physical laws of the universe that we must obey. We never doubt that. And so we just don't jump out of airplanes or jump off of high buildings for the fun of it—we don't do that. Because we unconsciously know that there is a final law of gravitation, and if you disobey it you'll suffer the consequences—we know that. Even if we don't know it in its Newtonian formulation, we know it intuitively, and so we just don't jump off the highest building in Detroit for the fun of it—we don't do that. Because we know that there is a law of gravitation which is final in the universe. (Lord) If we disobey it we'll suffer the consequences. But I'm not so sure if we know that there are moral laws just as abiding as the physical law. I'm not so sure about that. I'm not so sure if we really believe that there is a law of love in this universe, and that if you disobey it you'll suffer the consequences.“

—  Martin Luther King, Jr. American clergyman, activist, and leader in the American Civil Rights Movement 1929 - 1968

1950s, Rediscovering Lost Values (1954)

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„… very often the laws derived by physicists from a large number of observations are not rigorous, but approximate.“

—  Augustin Louis Cauchy French mathematician (1789–1857) 1789 - 1857

... très souvent les lois particulières déduites par les physiciens d'un grand nombre d'observations ne sont pas rigoureuses, mais approchées.
[Augustin Louis Cauchy, Sept leçons de physique, Bureau du Journal Les Mondes, 1868, 15]

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