An Assessment of Nature and Epistemic Roles of Principle of Non-Contradiction with Special Emphasis on Aristotle's Opinion

The main question addressed by this study is: What is Aristotle's formulation of the principle of non-contradiction and what are its epistemic roles? Using an analytic methodology and based on Aristotle's works this study assesses the nature and epistemic roles of the principle of non-contradiction. Based on this study, Aristotle has, on the whole, given seventeen formulations of the principle of non-contradiction. One can arrange these formulations into two groups: ontological formulations and logical formulations. The former focuses on 'existence' as the axis of the formulation of the principle of non-contradiction whereas the latter concentrates on the concepts of statement, negation and affirmation. According to this study, the ontological formulation of the principle of non-contradiction can be reduced to the opposition of words. Thus the limitations considered by Aristotle in his logical formulation of the principle of non-contradiction explain the unity of two concepts under all circumstance and the only difference they have is that one is negative in comparison to the other. Based on the findings of this research, Aristotle is of the view that in attaining knowledge the principle of non-contradiction is prior to any other type of knowledge whether notion or assertion. In other words, in Aristotle's philosophy the principle of non-contradiction is a principle (arche) for obtaining any other type of knowledge. The 'absolute priority' indicates that the principle of non-contradiction plays four epistemic roles which consist of justificatory base, indicatory base, signification base and practical base.