We can now recognize Aristotle\u27s many accomplishments in logical theory, not the least of which is treating the deduction process itself as a subject matter and thus establishing the science of logic. Aristotle took logic to be that part of epistemolo gy used to establish knowledge of logical consequence. Prior Analytics is a metalogical treatise on his syllogistic system in which Aristotle modelled his deduction system to demonstrate certain logical relationships among its rules. Aristotle\u27s n otion of substitution distinguishes logical syntax from semantics and enabled him to distinguish validity from deducibility sufficiently to note the completeness of his logic
