ABSTRACT
In his conclusion to his lectures on informal logic or theory of argumentation (Arist. Soph. el. 183 b 15 ff.) Aristotle declares with justified pride that he has established an entirely new discipline. With even greater justification this characterization might be applied to his syllogistics, the main portion of the formal logic. Plato’s logic was a logic of being, in which logic and metaphysics were inseparable. But Aristotle’s logic in its fully developed form is formal and concerns itself with the formal validity of logical inferences, which is to say with the relation between judgements, regardless of their content. On the one hand such a formal logic is thus delimited and set apart from metaphysics or science, and on the other hand from psychology. Formal logic does not examine how we think but deals with those abstract rules that are valid for correct thinking-whether anybody is thinking or not. From a modern point of view it is particularly significant that Aristotle refrains from any form of ‘psychologism’. Furthermore, since the Middle Ages a distinction between formal logic and linguistics has been generally accepted. Linguistics concerns itself with the actual structure of language, logic with the logical form of the linguistic expression and with the truth value of propositions. Aristotle himself does not always distinguish explicitly between linguistics and logic-in his time linguistics had not yet become an established science. Yet he was well aware that logical form and linguistic form are not readily identical, and in his syllogistics he does in practice maintain a distinction between the two. It reflects his understanding of the special nature of formal logic that he does not include it in his scientific system.
