Abstract

Traditionally, philosophers appealed to fundamental presuppositions they thought were central to the world view they were defending. Contemporary philosophy is not much interested in world views or fundamental presuppositions; yet, philosophers still appeal to presuppositions. My work examines presuppositions and their role within philosophy. ;I begin by explicating the concept of presupposition. Philosophers have often misconceived presupposition, conflating it with related concepts, such as assumption. I find reasons for preserving a distinction between presupposition and these related concepts. On my account of the nature of presupposition, it is a kind of necessary meaningfulness-condition. Analysis of the presupposition relation reveals it to be a logical relation holding primarily between semantic states and acts. ;Our commitments take many forms: to beliefs or statements being true or false, to experiences being veridical or not, to actions being rational or not, etc. For any commitment even to be meaningful , the committed person is logically committed to its presuppositions. In this way, presuppositional commitments are perhaps our most fundamental kind of logical commitment. We can reason back to presuppositions using ad hominem argumentation that discovers what we must be committed to given the meaningfulness of our commitments. ;There are levels of presuppositions. Some are internal to a conceptual system; others are part of the framework of a conceptual system. Most presuppositions are in principle avoidable by rejecting the commitments that carry them. But some presuppositions are unavoidable, because some conceptual systems are not contingent. There are presuppositions of basic and inescapable human activities or powers, such as reasoning itself. These transcendental presuppositions cannot be denied on pain of self-inconsistency. On this kind of basis, philosophers have claimed both that we can discover "categories" or categorial commitments revealing the basic structure of reality and that dialectical argumentation leads all to acknowledge these categorial commitments. The categorial truths philosophy establishes in this manner provide an important objective foundation for philosophy and the culture