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Who said: “I have no satisfaction in formulas unless I feel their arithmetical magnitude.”
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Thumbnail of Claude Bernard (source)
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.

Claude Bernard - Context of quote
“The experimenter who does not know…”

Illustrated Quote - Large (800 x 600 px)

Thumbnail detail from illustration in The Ordinal of Alchemy c.1477, British Library
Alchemist c.1477 (source)
“The experimenter who does not know what he is looking for will never understand what he finds.”
— Claude Bernard

More Claude Bernard quotes on science >>

This quote is one of those tantalizingly known only as “attributed.” Any original quote by Bernard would presumably be in his native French language, which makes tracking the source down more difficult. It is also seen1 as:

He who does not know what he is looking for will not lay hold of what he has found when he gets it.

A related idea appears in Bernard’s book, Introduction à l'étude de la médecine expérimentale (1865). As translated2, he says: “L’ecueil de I’expérimentateur consistera donc à croire connaître ce qu’il ne connaît pas, et à prendre pour des vérités absolues des vérités qui ne sont que relatives.”

The pitfall of the experimenter consists in believing that which he does not know, and taking as absolute truths those truths which are only relative.

If you know the primary source of the attributed quote, please contact the Webmaster.

1 As quoted by Sir Michael Foster, in Masters of Medicine, Vol. 1, Claude Bernard (1899), 228, without citation.
2 Claude Bernard, Introduction à l'étude de la médecine expérimentale (1865), 86. As translated by Webmaster. Also see translation by A.S. Weber, in his Nineteenth-Century Science: An Anthology (2000), 317.

Text by Webmaster. The subject quote appears, for example, in John Farley, The Spontaneous Generation Controversy from Descartes to Oparin (1977), 3, but without citation. (source)

See also:
  • Science Quotes by Claude Bernard.
  • 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 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)

Nature bears long with those who wrong her. She is patient under abuse. But when abuse has gone too far, when the time of reckoning finally comes, she is equally slow to be appeased and to turn away her wrath. (1882) -- Nathaniel Egleston, who was writing then about deforestation, but speaks equally well about the danger of climate change today.
Carl Sagan Thumbnail Carl Sagan: 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) ...(more by Sagan)

Albert Einstein: I used to wonder how it comes about that the electron is negative. Negative-positive—these are perfectly symmetric in physics. There is no reason whatever to prefer one to the other. Then why is the electron negative? I thought about this for a long time and at last all I could think was “It won the fight!” ...(more by Einstein)

Richard Feynman: It is the facts that matter, not the proofs. Physics can progress without the proofs, but we can't go on without the facts ... if the facts are right, then the proofs are a matter of playing around with the algebra correctly. ...(more by Feynman)
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