1. The art of critical examination into the truth of an opinion; the investigation of truth by discussion: in earlier English use, a synonym of logic as applied to formal rhetorical reasoning; logical argumentation or disputation.
2. In modern Philosophy; specifically applied by Kant to the criticism which shows the mutually contradictory character of the principles of science, when they are employed to determine objects beyond the limits of experience (i.e. the soul, the world, God); by Hegel (who denies that such contradictions are ultimately irreconcilable) the term is applied:

• To the process of thought by which such contradictions are seen to merge themselves in a higher truth that comprehends them.
• To the world-process, which, being in his view but the thought-process on its objective side, develops similarly by a continuous unification of opposites.