The process of knowledge from the general to the particular, which is peculiar to the sciences, involves the necessity that in the sciences much should be established by deduction from preceding propositions, that is to say, by demonstration; and this has given rise to the old mistake that only what has been demonstrated is absolutely true, and that every truth requires a demonstration;
-Zientzien bereizgarria den ezagutzaren bide horrek, orokorretik partikularrerakoak, berekin dakar, horietan gauza asko aurreko printzipioetatik dedukzioz, baita frogapenen bitartez oinarrituak egotea ere, eta horrek sorrarazi du errore zaharra, egia frogaturikoa bakarrik delakoa eta egia orok frogapen bat behar duelakoa;