Claude Bernard


French Physiologist

Author Quotes

Man is forced to be free for this reason alone; that he has a conscience and judgement. His liberty flows from this. He is free to do good or bad; but when he has done bad, remorse proves to him that he was free, and that he could have done otherwise, had he so wished.

Proof that a given condition always precedes or accompanies a phenomenon does not warrant concluding with certainty that a given condition is the immediate cause of that phenomenon. It must still be established that when this condition is removed, the phenomena will no longer appear.

The eloquence of a scientist is clarity; scientific truth is always more luminous when its beauty is unadorned than when it is tricked out in the embellishments with which our imagination would seek to clothe it.

The origin of an original work is always the pursuit of a fact which does not fit into accepted ideas.

Today no one says any longer 'it is good; that is fine'. No one believes in himself. He says it will sell - or it will not sell.

When entering on new ground we must not be afraid to express even risky ideas so as to stimulate research in all directions. As Priestley put it, we must not remain inactive through false modesty based on fear of being mistaken.

Hatred is the most clear- sighted, next to genius

In the philosophic sense, observation shows and experiment teaches.

Mediocre men often have the most acquired knowledge

Put off your imagination, as you put off your overcoat, when you enter the laboratory. Put it on again, as you put on your overcoat, when you leave.

The experiment is complete only after the counterproof, just as analysis is never complete except after synthesis. In physiology we cannot make a synthesis, but we can carry out the control experiment - or counterproof.

The physiologist is not a man of the world, he is a scientist, a man caught and absorbed by a scientific idea that he pursues; he no longer hears the cries of the animals, no longer sees the flowing blood, he sees only his idea: organisms that hide from him problems that he wants to discover. He doesn't feel that he is in a horrible carnage; under the influence of a scientific idea, he pursues with delight a nervous filament inside stinking and livid flesh that for any other person would be an object of disgust and horror.

Tout est poison, rien n'est poison, tout est une question de dose. Everything is poisonous, nothing is poisonous, it is all a matter of dose.

When he does not know what he ought to want, he should know what his enemy wants - and want the contrary.

I am convinced that I have also served science in this way: I have stimulated work

In the sciences, there is doubtless a very close connection between observation and experimentation. Nevertheless, it is necessary to distinguish them because (otherwise) everything would become confused.

Mediocre men often have the most acquired knowledge. It is in the darker. It is in the darker regions of science that great men are recognized; they are marked by ideas which light up phenomena hitherto obscure and carry science forward.

Real science exists, then, only from the moment when a phenomenon is accurately defined as to its nature and rigorously determined in relation to its material conditions, that is, when its law is known. Before that, we have only groping and empiricism.

The experimenter who does not know what he is looking for will never understand what he finds.

The science of life is a superb and dazzlingly lighted hall which may be reached only by passing through a long and ghastly kitchen.

True science teaches us to doubt and to abstain from ignorance.

When one calls a new fact a discovery, the fact itself is not a discovery, but rather the new idea derived from it.

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.

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.

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.

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French Physiologist