Although Plato and Euclid, both pupils of Socrates, were probably the first two men to seriously contemplate logical problems, Aristotle's Organon represents the first systematic treatment of the subject in the history of philosophy. Likewise, Aristotle 1_s Rhetoric contains the first systematic adaptation of the principles of logic to the art of public address. Since that time, rhetoricians have continued to incorporate writings in logic into rhetorical theory. Formal logic, the philosophy of induction and scientific method, and more recently, the Toulmin structural model for argument, all have found a place in modern works in argumentation and debate. In addition, many writers in speech have gone beyond their philosophical heritage and introduced new types and uses of argument which are particularly suited to the needs of the public speaker. The resultant treatment given the definition and nature of argument by writers in speech provides the primary theoretical foundation which underlies the study of argumentation and, more broadly, the process of debate.