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Line 10: That the concept of form is fundamental to logic was already recognized in ancient times. [[Aristotle]] was probably the first to employ variable letters to represent valid inferences (in the [[Prior analytics]]). (For which reason [[Jan Łukasiewicz\|Łukasiewicz]] says that the introduction of variables was 'one of Aristotle's greatest inventions'). According to the followers of Aristotle (such as [[Ammonius Hermiae\|Ammonius]]), only the logical principles stated in schematic terms belong to logic, and not those given in concrete terms. The concrete terms ''man'', ''mortal'', &cetc., are analogous to the substitution values of the schematic placeholders 'A', 'B', 'C', which were called the 'matter' (Greek ''hyle'', Latin ''materia'') of the argument. ==See also==

Logical form: Difference between revisions