This 11th-grade unit on language of discourse is designed to help students gain the ability to evaluate argument, to construct logical and reasonable discourse, and to recognize ethical standards of free speech and inquiry. Stephen Toulmin's model of "evidence-warrant-claim" is used as a basic pattern for both the evaluation and construction of argument. The nature of proof (motivational, authoritative, and substantive) is then reviewed with a particular focus on (1) lines of argument--e.g., causality, generalization, and analogy, (2) varieties of proof--e.g., fact and opinion, and (3) tests for logical adequacy--e.g., clarity, internal and external consistency, and verifiability. Finally, the ethics of argument, or the ends and means of persuasion, are determined. Readings from such sources as Walter Lippman, David Lloyd George, and Mark Twain are analyzed, and students are asked to develop speeches and essays using the various approaches they have learned. Included are procedural notes, lectures, sample discussion questions and answers, worksheets, and suggested student activities. (JB)