Jefferson, Letter to Henry Lee, May 8, 1825.
Harrington, Oceana, The Preliminaries.
Aristotle’s reliance on endoxa takes on a still greatersignificance given the role such opinions play in dialectic,which he regards as an important form of non-scientificreasoning. Dialectic, like science(epistêmê), trades in logical inference; butscience requires premises of a sort beyond the scope of ordinarydialectical reasoning. Whereas science relies upon premises whichare necessary and known to be so, a dialectical discussion can proceedby relying on endoxa, and so can claim only to be as secure asthe endoxa upon which it relies. This is not a problem,suggests Aristotle, since we often reason fruitfully and well incircumstances where we cannot claim to have attained scientificunderstanding. Minimally, however, allreasoning—whether scientific or dialectical—must respectthe canons of logic and inference.
Sidney, Discourses concerning Government, section 15.
Among the great achievements to which Aristotle can lay claim is thefirst systematic treatment of the principles of correct reasoning, thefirst logic. Although today we recognize many forms of logicbeyond Aristotle’s, it remains true that he not only developed atheory of deduction, now called syllogistic, but added to it a modalsyllogistic and went a long way towards proving some meta-theoremspertinent to these systems. Of course, philosophers beforeAristotle reasoned well or reasoned poorly, and the competent among themhad a secure working grasp of the principles of validity andsoundness in argumentation. No-one before Aristotle, however, developed asystematic treatment of the principles governing correct inference; andno-one before him attempted to codify the formal and syntacticprinciples at play in such inference. Aristotle somewhatuncharacteristically draws attention to this fact at the end of adiscussion of logic inference and fallacy: