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

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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.



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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A fact is nothing in itself. It has value only for the idea connected with it or through the proof that it furnishes.
— Claude Bernard
In An Introduction to the Study of Experimental Medicine (1927, 1957), 53, as translated by Henry Copley Greene. From the original French by Claude Bernard: “Un fait n’est rien par lui-même, il ne vaut que par l’idée qui s’y rattache ou par la preuve qu’il fournit.” (1865), 93.
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A great surgeon performs operations for stone by a single method; later he makes a statistical summary of deaths and recoveries, and he concludes from these statistics that the mortality law for this operation is two out of five. Well, I say that this ratio means literally nothing scientifically and gives us no certainty in performing the next operation; for we do not know whether the next case will be among the recoveries or the deaths. What really should be done, instead of gathering facts empirically, is to study them more accurately, each in its special determinism. We must study cases of death with great care and try to discover in them the cause of mortal accidents so as to master the cause and avoid the accidents.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 137-138. (Note that Bernard overlooks how the statistical method can be useful: a surgeon announcing a mortality rate of 40% invites comparison. A surgeon with worse outcomes should adopt this method. If a surgeon has a better results, that method should be adopted.)
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Ardent desire for knowledge, in fact, is the one motive attracting and supporting investigators in their efforts; and just this knowledge, really grasped and yet always flying before them, becomes at once their sole torment and their sole happiness. Those who do not know the torment of the unknown cannot have the joy of discovery which is certainly the liveliest that the mind of man can ever feel.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1927, 1957), 221-222, as translated by Henry Copley Greene. From the original French by Claude Bernard: “Le désir ardent de la connaissance est l’unique mobile qui attire et soutient l’investigateur dans ses efforts; et c’est précisément cette connaissance qu’il saisit réellement et qui fuit cependant toujours devant lui, qui devient à la fois son seul tourment et son seul bonheur. Celui qui ne connaît pas les tourments de l’inconnu doit ignorer les joies de la découverte qui sont certainement les plus vives que l’esprit de l’homme puisse jamais ressentir.” (1865), 388. A Google translation gives: “The ardent desire for knowledge is the only motive which attracts and sustains the inquirer in his efforts; and it is precisely this knowledge which he really grasps and which nevertheless always flees before him, which becomes at the same time his only torment and his only happiness. He who does not know the torments of the unknown must ignore the joys of discovery which are certainly the most vivid that the mind of man can ever experience.”
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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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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 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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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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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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Negative facts when considered alone never teach us anything.
— Claude Bernard
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Progress is achieved by exchanging our theories for new ones which go further than the old, until we find one based on a larger number of facts. … Theories are only hypotheses, verified by more or less numerous facts. Those verified by the most facts are the best, but even then they are never final, never to be absolutely believed.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 165.
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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 first requirement in using statistics is that the facts treated shall be reduced to comparable units.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 136.
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The goal of scientific physicians in their own science … is to reduce the indeterminate. Statistics therefore apply only to cases in which the cause of the facts observed is still indeterminate.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 139.
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Theories are like a stairway; by climbing, science widens its horizon more and more, because theories embody and necessarily include proportionately more facts as they advance.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 165.
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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 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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Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1865), as translated by Henry Copley Greene (1957), 165.
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When we meet a fact which contradicts a prevailing theory, we must accept the fact and abandon the theory, even when the theory is supported by great names and generally accepted.
— Claude Bernard
From An Introduction to the Study of Experimental Medicine (1927, 1957), 164, as translated by Henry Copley Greene. From the original French by Claude Bernard: “Quand le fait qu’on rencontre est en opposition avec une théorie régnante, il faut accepter le fait et abandonner la théorie, lors même que celle-ci, soutenue par de grands noms, est généralement adoptée.” (1865), 287-288. A Google translation gives: “When the fact one encounters is in opposition to a reigning theory, one must accept the fact and abandon the theory, even when the latter, supported by great names, is generally adopted.”
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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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