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Home > Dictionary of Science Quotations > Scientist Names Index B > Claude Bernard Quotes > Experiment

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Claude Bernard
(12 Jul 1813 - 10 Feb 1878)

French physiologist who helped establish the principles of experimentation in the life sciences. His Introduction to the Study of Experimental Medicine (1865) is a scientific classic.



A l’aide de ces sciences expérimentales actives, l’homme devient un inventeur de phénomènes, un véritable contremaître de la création; et l'on ne saurait, sous ce rapport, assigner de limites à la puissance qu’il peut acquérir sur la nature, par les progrès futurs des sciences expérimentales
With the aid of these active experimental sciences man becomes an inventor of phenomena, a real foreman of creation; and under this head we cannot set limits to the power that he may gain over nature through future progress of the experimental sciences.
— Claude Bernard
Original French text in Introduction à l'Étude de la Médecine Expérimentale (1898), 32. English version from An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 18.
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Il ne fallait jamais faire des expériences pour confirmer ses idées, mais simplement pour les contrôler.
We must never make experiments to confirm our ideas, but simply to control them.
— Claude Bernard
From Introduction à l'étude de la médecine expérimentale (1865), 67-68. Translation from Henry Copley Green, An Introduction to the Study of Experimental Medicine (1957), 38. Bernard footnoted that he had expressed this idea earlier in Leçons sur les propriétés et les altérations des liquides de l’organisme (1859), Première leçon.
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La théorie est l’hypothèse vérifiée, après qu’elle a été soumise au contrôle du raisonnement et de la critique expérimentale. La meilleure théorie est celle qui a été vérifiée par le plus grand nombre de faits. Mais une théorie, pour rester bonne, doit toujours se modifier avec les progrès de la science et demeurer constamment soumise à la vérification et à la critique des faits nouveaux qui apparaissent.
A theory is a verified hypothesis, after it has been submitted to the control of reason and experimental criticism. The soundest theory is one that has been verified by the greatest number of facts. But to remain valid, a theory must be continually altered to keep pace with the progress of science and must be constantly resubmitted to verification and criticism as new facts appear.
— Claude Bernard
Original work in French, Introduction à l'Étude de la Médecine Expérimentale (1865), 385. English translation by Henry Copley Green in An Introduction to the Study of Experimental Medicine (1927, 1957), 220.
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La théorie n’est que l’idée scientifique contrôlée par l’expérience.
A theory is merely a scientific idea controlled by experiment.
— Claude Bernard
Original work in French, Introduction à l'Étude de la Médecine Expérimentale (1865), 40. English translation by Henry Copley Green in An Introduction to the Study of Experimental Medicine (1927, 1957), 26.
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Une idée anticipée ou une hypothèse est donc le point de départ nécessaire de tout raisonnement expérimental. Sans cela on ne saurait faire aucune investigation ni s’instruire ; on ne pourrait qu’entasser des observations stériles. Si l’on expérimentait sans idée préconçue, on irait à l’aventure; mais d’un autre côté, ainsi que nous l’avons dit ailleurs, si l’on observait avec des idées préconçues, on ferait de mauvaises observations.
An anticipative idea or an hypothesis is, then, the necessary starting point for all experimental reasoning. Without it, we could not make any investigation at all nor learn anything; we could only pile up sterile observations. If we experimented without a preconceived idea, we should move at random.
[Also seen translated as:] A hypothesis is … the obligatory starting point of all experimental reasoning. Without it no investigation would be possible, and one would learn nothing: one could only pile up barren observations. To experiment without a preconceived idea is to wander aimlessly.
— Claude Bernard
Original work in French, Introduction à l'Étude de la Médecine Expérimentale (1865). English translation by Henry Copley Green in An Introduction to the Study of Experimental Medicine (1927, 1957), 32. Alternate translation in Peter Medawar, 'Hypothesis and Imagination', collected in The Strange Case of the Spotted Mice and Other Classic Essays on Science (1974), 30.
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A physician’s subject of study is necessarily the patient, and his first field for observation is the hospital. But if clinical observation teaches him to know the form and course of diseases, it cannot suffice to make him understand their nature; to this end he must penetrate into the body to find which of the internal parts are injured in their functions. That is why dissection of cadavers and microscopic study of diseases were soon added to clinical observation. But to-day these various methods no longer suffice; we must push investigation further and, in analyzing the elementary phenomena of organic bodies, must compare normal with abnormal states. We showed elsewhere how incapable is anatomy alone to take account of vital phenenoma, and we saw that we must add study of all physico-chemical conditions which contribute necessary elements to normal or pathological manifestations of life. This simple suggestion already makes us feel that the laboratory of a physiologist-physician must be the most complicated of all laboratories, because he has to experiment with phenomena of life which are the most complex of all natural phenomena.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 140-141.
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As soon as the circumstances of an experiment are well known, we stop gathering statistics. … The effect will occur always without exception, because the cause of the phenomena is accurately defined. Only when a phenomenon includes conditions as yet undefined,Only when a phenomenon includes conditions as yet undefined, can we compile statistics. … we must learn therefore that we compile statistics only when we cannot possibly help it; for in my opinion, statistics can never yield scientific truth.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 134-137.
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By destroying the biological character of phenomena, the use of averages in physiology and medicine usually gives only apparent accuracy to the results. From our point of view, we may distinguish between several kinds of averages: physical averages, chemical averages and physiological and pathological averages. If, for instance, we observe the number of pulsations and the degree of blood pressure by means of the oscillations of a manometer throughout one day, and if we take the average of all our figures to get the true or average blood pressure and to learn the true or average number of pulsations, we shall simply have wrong numbers. In fact, the pulse decreases in number and intensity when we are fasting and increases during digestion or under different influences of movement and rest; all the biological characteristics of the phenomenon disappear in the average. Chemical averages are also often used. If we collect a man's urine during twenty-four hours and mix all this urine to analyze the average, we get an analysis of a urine which simply does not exist; for urine, when fasting, is different from urine during digestion. A startling instance of this kind was invented by a physiologist who took urine from a railroad station urinal where people of all nations passed, and who believed he could thus present an analysis of average European urine! Aside from physical and chemical, there are physiological averages, or what we might call average descriptions of phenomena, which are even more false. Let me assume that a physician collects a great many individual observations of a disease and that he makes an average description of symptoms observed in the individual cases; he will thus have a description that will never be matched in nature. So in physiology, we must never make average descriptions of experiments, because the true relations of phenomena disappear in the average; when dealing with complex and variable experiments, we must study their various circumstances, and then present our most perfect experiment as a type, which, however, still stands for true facts. In the cases just considered, averages must therefore be rejected, because they confuse, while aiming to unify, and distort while aiming to simplify. Averages are applicable only to reducing very slightly varying numerical data about clearly defined and absolutely simple cases.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 134-135.
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Experiment is fundamentally only induced observation.
— Claude Bernard
Section title in An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 19.
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I do not … reject the use of statistics in medicine, but I condemn not trying to get beyond them and believing in statistics as the foundation of medical science. … Statistics … apply only to cases in which the cause of the facts observed is still [uncertain or] indeterminate. … There will always be some indeterminism … in all the sciences, and more in medicine than in any other. But man’s intellectual conquest consists in lessening and driving back indeterminism in proportion as he gains ground for determinism by the help of the experimental method..
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 138-140.
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In a word, I consider hospitals only as the entrance to scientific medicine; they are the first field of observation which a physician enters; but the true sanctuary of medical science is a laboratory; only there can he seek explanations of life in the normal and pathological states by means of experimental analysis.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 146.
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In sciences of observation, man observes and reasons experimentally, but he does not experiment; and in this sense we might say that a science of observation is a passive science. In sciences of experimentation, man observes, but in addition he acts on matter, analyzes its properties and to his own advantage brings about the appearance of phenomena which doubtless always occur according to natural laws, but in conditions which nature often has not yet achieved. With the help of these active experimental sciences, man becomes an inventor of phenomena, a real foreman of creation; and under this head we cannot set limits to the power that he may gain over nature through future progress in the experimental sciences.
— Claude Bernard
From Introduction à l'Étude de la Médecine Expérimentale (1865); as translated by Henry Copley Greene, in An Introduction to the Study of Experimental Medicine (1927, 1957), 18. As given, for example, in Fielding Hudson Garrison, An Introduction to the History of Medicine (1929), 15. Compare the (apparent?) summary of this quote, expressed as, “Observation is a passive science, experimentation is an active science.” The shorter quote is seen for example, in Fielding Hudson Garrison, An Introduction to the History of Medicine (1929), 15. However, Webmaster has not yet found these few words verbatim in a primary source, and believes although the shortened quote is a summary, in very few words, of the idea expressed in the longer passage above, that it was not written verbatim by Bernard himself.
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In teaching man, experimental science results in lessening his pride more and more by proving to him every day that primary causes, like the objective reality of things, will be hidden from him forever and that he can only know relations.
— Claude Bernard
…...
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In the philosophic sense, observation shows and experiment teaches.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 5.
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In these researches I followed the principles of the experimental method that we have established, i.e., that, in presence of a well-noted, new fact which contradicts a theory, instead of keeping the theory and abandoning the fact, I should keep and study the fact, and I hastened to give up the theory.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 164.
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It is impossible to devise an experiment without a preconceived idea; devising an experiment, we said, is putting a question; we never conceive a question without an idea which invites an answer. I consider it, therefore, an absolute principle that experiments must always be devised in view of a preconceived idea, no matter if the idea be not very clear nor very well defined.
— Claude Bernard
An Introduction to the Study of Experimental Medicine (1865, translation 1927, 1957), 23.
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Laplace considers astronomy a science of observation, because we can only observe the movements of the planets; we cannot reach them, indeed, to alter their course and to experiment with them. “On earth,” said Laplace, “we make phenomena vary by experiments; in the sky, we carefully define all the phenomena presented to us by celestial motion.” Certain physicians call medicine a science of observations, because they wrongly think that experimentation is inapplicable to it.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 18. A footnote cites Laplace, Système du monde, Chap. 2.
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Man does not limit himself to seeing; he thinks and insists on learning the meaning of phenomena whose existence has been revealed to him by observation. So he reasons, compares facts, puts questions to them, and by the answers which he extracts, tests one by another. This sort of control, by means of reasoning and facts, is what constitutes experiment, properly speaking; and it is the only process that we have for teaching ourselves about the nature of things outside us.
— Claude Bernard
In Claude Bernard and Henry Copley Greene (trans.), An Introduction to the Study of Experimental Medicine (1927, 1957), 5.
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Man is naturally metaphysical and arrogant, and is thus capable of believing that the ideal creations of his mind, which express his feelings, are identical with reality. From this it follows that the experimental method is not really natural to him.
— Claude Bernard
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Men who believe too firmly in their theories, do not believe enough in the theories of others. So … these despisers of their fellows … make experiments only to destroy a theory, instead of to seek the truth.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1927, 1957), as translated by Henry Copley Greene (1957), 38. From the original French by Claude Bernard: “Ceux qui croient trop à leurs théories ne croient pas assez à celles des autres. Alors … ces contempteurs d'autrui … font des expériences que pour détruire une théorie, au lieu de les faire pour chercher la vérité.” (1865), 68. A Google translation gives: “Those who believe too much in their theories do not believe enough in those of others. So … these despisers of others … do experiments only to destroy a theory, instead of doing them to seek the truth.”
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Men who have excessive faith in their theories … make poor observations, because they choose among the results of their experiments only what suits their object, neglecting whatever is unrelated to it and carefully setting aside everything which might tend toward the idea they wish to combat.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1927, 1957), as translated by Henry Copley Greene (1957), 38. Note: the ellipsis condenses the quote from two paragraphs, beginning with the same clause as another quote on this web page, beginning, “Men who have excessive faith….” From the original French by Claude Bernard: “Les hommes qui ont une foi excessive dans leurs théories … font de mauvaises observations parce qu'ils ne prennent dans les résultats de leurs expériences que ce qui convient à leur but en négligeant ce qui ne s'y rapporte pas, et en écartant bien soigneusement tout ce qui pourrait aller dans le sens de l'idée qu'ils veulent combattre.” (1865), 67-68. A Google translation gives: “Men who have excessive faith in their theories … make bad observations because they only take from the results of their experiments what suits their purpose, neglecting what does not relate to it, and carefully discarding everything that could go in the direction of the idea they want to fight.”
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Men who have excessive faith in their theories or ideas are not only ill prepared for making discoveries; they also make very poor observations. Of necessity, they observe with a preconceived idea, and when they devise an experiment, they can see, in its results,only a confirmation of their theory. In this way they distort observation and often neglect very important facts because they do not further their aim.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1927, 1957), as translated by Henry Copley Greene (1957), 38. From the original French by Claude Bernard: “Les hommes qui ont une foi excessive dans leurs théories ou dans leurs idées sont non-seulement mal disposés pour faire des découvertes, mais ils font aussi de très-mauvaises observations. Ils observent nécessairement avec une idée préconçue, et quand ils ont institué une expérience, ils ne veulent voir dans ses résultats qu'une confirmation de leur théorie. Ils défigurent ainsi l'observation et négligent souvent des faits très-importants, parce qu’ils ne concourent pas à leur but.” (1865), 68. A Google translation gives: “Men who have excessive faith in their theories or in their ideas are not only ill disposed to make discoveries, but they also make very bad observations. They necessarily observe with a preconceived idea, and when they have instituted an experiment, they only want to see in its results a confirmation of their theory. They thus disfigure observation and often neglect very important facts, because they do not contribute to their end.”
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Observation is a passive science, experimentation is an active science.
— Claude Bernard
As given, for example, in Fielding Hudson Garrison, An Introduction to the History of Medicine (1929), 15. Webmaster has not found these words verbatim in a primary source, and believes there are summary of an idea expressed in a longer passage. See the quotation beginning “In sciences of observation,” elsewhere on this web page. From Introduction à l'Étude de la Médecine Expérimentale (1865); as translated by Henry Copley Greene, in An Introduction to the Study of Experimental Medicine (1927), 18.
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One must accept the results of experiments as they come, with all their unexpectedness and irregularity.
— Claude Bernard
In An Introduction to the Study of Experimental Medicine (1927, 1957), 38, as translated by Henry Copley Greene. From the original French by Claude Bernard: “il faut accepter les résultats de l'expérience tels qu'ils se présentent, avec tout leur imprévu et leurs accidents.” (1865), 68. A Google translation gives: “One must accept the results of the experiment as they present themselves, with all their unforeseen and their accidents.”
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Speaking concretely, when we say “making experiments or making observations,” we mean that we devote ourselves to investigation and to research, that we make attempts and trials in order to gain facts from which the mind, through reasoning, may draw knowledge or instruction.
Speaking in the abstract, when we say “relying on observation and gaining experience,” we mean that observation is the mind's support in reasoning, and experience the mind's support in deciding, or still better, the fruit of exact reasoning applied to the interpretation of facts. It follows from this that we can gain experience without making experiments, solely by reasoning appropriately about well-established facts, just as we can make experiments and observations without gaining experience, if we limit ourselves to noting facts.
Observation, then, is what shows facts; experiment is what teaches about facts and gives experience in relation to anything.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 11.
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The doubter is a true man of science: he doubts only himself and his interpretations, but he believes in science.
— Claude Bernard
In Fielding Hudson Garrison, An Introduction to the History of Medicine (1929), 14.
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The experimenter who does not know what he is looking for will never understand what he finds.
— Claude Bernard
Attributed. Also seen as, “He who does not know what he is looking for will not lay hold of what he has found when he gets it.” If you know a primary source, perhaps in the original French, please contact Webmaster.
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The great experimental principle, then, is doubt, that philosophic doubt which leaves to the mind its freedom and initiative, and from which the virtues most valuable to investigators in physiology and medicine are derived.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 37.
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The true worth of an experimenter consists in his pursuing not only what he seeks in his experiment, but also what he did not seek.
— Claude Bernard
Unverified in these exact words. Contact webmaster if you know the primary source. Perhaps the quote is a summary of a longer passage. Claude lays out his experimental philosophy in An Introduction to the Study of Experimental Medicine (1865).
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To be worthy of the name, an experimenter must be at once theorist and practitioner. While he must completely master the art of establishing experimental facts, which are the materials of science, he must also clearly understand the scientific principles which guide his reasoning through the varied experimental study of natural phenomena. We cannot separate these two things: head and hand. An able hand, without a head to direct it, is a blind tool; the head is powerless without its executive hand.
— Claude Bernard
In Claude Bernard and Henry Copley Greene (trans.), An Introduction to the Study of Experimental Medicine (1927, 1957), 3.
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We must trust our observations or our theories only after experimental verification. If we trust too much, the mind becomes bound and cramped by the results of its own reasoning; it no longer has freedom of action, and so lacks the power to break away from that blind faith in theories which is only scientific superstition.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 37.
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We see, then, that the elements of the scientific method are interrelated. Facts are necessary materials; but their working up by experimental reasoning, i.e., by theory, is what establishes and really builds up science. Ideas, given form by facts, embody science. A scientific hypothesis is merely a scientific idea, preconceived or previsioned. A theory is merely a scientific idea controlled by experiment. Reasoning merely gives a form to our ideas, so that everything, first and last, leads back to an idea. The idea is what establishes, as we shall see, the starting point or the primum movens of all scientific reasoning, and it is also the goal in the mind's aspiration toward the unknown.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 26.
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See also:
  • 12 Jul - short biography, births, deaths and events on date of Bernard's birth.
  • Claude Bernard - context of quote The alchemists founded chemistry - Medium image (500 x 350 px)
  • Claude Bernard - context of quote “The alchemists founded chemistry” - Large image (800 x 600 px)
  • Claude Bernard - context of quote The experimenter - Medium image (500 x 350 px)
  • Claude Bernard - context of quote The experimenter - Large image (800 x 600 px)
  • Claude Bernard - context of quote Make experiments to … control our ideas - Medium image (500 x 350 px)
  • Claude Bernard - context of quote Make experiments to … control our ideas - Large image (800 x 600 px)

Carl Sagan Thumbnail In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan
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