Abstract
At the outset, the philosopher being challenged hopes that the whole question rests on a false assumption. Maybe one can in fact fit together all of the doctrines of major philosophers in a single system which will be consistent, and so prove that there is no contradiction? But that plan hits a snag almost at once: for there are types of philosophic system so related that whenever a given proposition is true in one, its contrary is true in the other. Sextus Empiricus was particularly ingenious at arranging these dual positions in parallel column, but even without his help, brief experiment shows that a simple conjunction rule will not answer the skeptic’s question.