But it happens further quite naturally that men who believe too firmly in their theories, do not believe enough in the theories of others. So the dominant idea of these despisers of their fellows is to find others’ theories faulty and to try to contradict them. […] They make experiments only to destroy a theory, instead of to seek the truth. At the same time, they 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 they idea they wish to combat.

[Mais il arrive encore tout naturellement que ceux qui croient trop à leurs théories ne croient pas assez à celles des autres. Alors l’idée dominante de ces contempteurs d’autrui est de trouver les théories des autres en défaut et de chercher à les contredire. […] Ils ne font des expériences que pour détruire une théorie, au lieu de les faire pour chercher la vérité. Ils font également 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.]

Claude Bernard (1813-1878) French physiologist, scientist

An Introduction to the Study of Experimental Medicine [Introduction à l’Étude de la Médecine Expérimentale], ch. 3 (1865) [tr. Greene (1957)]
    (Source)

(Source (French)). Other translation:

But it still happens quite naturally that those who believe too strongly in their own theories don't believe enough in those of others. The dominant idea of ​​these detractors of others is to find flaws in other people's theories and to try to contradict them. [...] They conduct experiments only to disprove a theory, instead of doing so to seek the truth. They also make flawed observations because they only select from the results of their experiments what suits their purpose, neglecting what is irrelevant, and carefully disregarding anything that might support the idea they want to refute.
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