This dissertation argues that recent theoretical attempts to understand fallacious reasoning fail because these theories presuppose problematic accounts of the nature of argument. Current fallacy theories agree that a fallacy is a mistake, but differ wildly about what sort of mistake it is. Chapters one through three explore three very different suggestions. Chapter one is devoted to an examination of the oldest of the modern theoretical accounts of fallacious reasoning, what Hamblin calls the standard treatment. Chapter two begins with a (...) discussion of Finocchiaro's skeptical argument against the very possibility of a fallacy theory. It then turns to a discussion of van Eemeren and Grootendorst's pragma-dialectical treatment of fallacious reasoning as a possible response to Finocchiaro's skeptical challenge. Chapter three examines two epistemic responses to Finocchiaro's analysis: Fogelin and Duggan's frequency treatment and Wreen's mistaken inference treatment. The first three chapters set the stage for an alternative account of fallacies developed in chapter four. This alternative view of fallacious reasoning is consistent with Wright's recent work on the concept of an argument. It suggests that fallacious reasoning results from a kind of incompetency. Such failures of competency, however, are not nearly as common as traditional accounts of fallacious reasoning suggests. Moreover, the very possibility of being tempted by fallacious reasoning depends on our being very competent in normal cases. Chapter four ends with a discussion of some of the implications of this alternative theory of fallacious reasoning for the way we understand and teach argument and reasoning. (shrink)