The Aims of the Book -/- 1. To improve your skill in analyzing and evaluating arguments and presentations of the kind you find in everyday discourse (news media, discussions, advertisements), textbooks, and lectures. 2. To improve your skill in presenting arguments, reports and instructions clearly and persuasively. 3. To improve your critical instincts, that is, your immediate judgments of your attitudes toward the communications and behavior of others and yourself, so that you consistently approach them with the standards of reason (...) and the attitude of reasonableness. 4. To improve your knowledge about the facts and arguments relevant to a large number of important contemporary issues in politics, education, ethics, and several practical fields. -/- These are practical aims but not narrow practical aims: the third one, in particular, is very far-reaching and requires a whole shift of values for most of us. So this is intended to be a powerful, as well as practical, book using practical, everyday examples of the kind that a citizen, especially a citizen-student, runs into all the time. -/- The text starts with a short discussion of reasoning itself, then explores the details of this approach, and then gets down to practical procedures for improving one's reasoning skills. The discussions and examples always begin at a rather elementary level, but they get into harder material fairly quickly. If you are, or are hoping to be, a teacher or a lawyer, a scientist or an executive, what you learn here will be professional skills for you—vital professional skills. But for any citizen, they are also essential skills. (shrink)

In their book EVALUATING CRITICAL THINKING Stephen Norris and Robert Ennis say: “Although it is tempting to think that certain [unstated] assumptions are logically necessary for an argument or position, they are not. So do not ask for them.” Numerous writers of introductory logic texts as well as various highly visible standardized tests (e.g., the LSAT and GRE) presume that the Norris/Ennis view is wrong; the presumption is that many arguments have (unstated) necessary assumptions and that readers and test takers (...) can reasonably be expected to identify such assumptions. This paper proposes and defends criteria for determining necessary assumptions of arguments. Both theoretical and empirical considerations are brought to bear. (shrink)

Any enthymeme can be made logically valid by adding as a suppressed premise a conditional that reiterates the argument's stated content and inferential structure in if-then form, We cannot blanketly prohibit reiteration to avoid this sort of trivialization, because some enthymemes legitimately require completion by reiterative conditionals, The solution proposed here is to allow reiterative expansions, but to rank them, other things being equal, as less charitable than nonreiterative expansions. Reiterative expansions can then be chosen as the most charitable only (...) when all nonreiterative expansions have been eliminated for independent reasons. This pluralistic model encourages experimentation with a number of different permissible expansions in evaluating enthymemes, from the least controversial or problematic to the most trivializing and the least charitable. (shrink)

Identifying the missing or unstated premisses of arguments is important, because their logical quality depends on them. Textbook authors regard enthymematic syllogisms (e.g., "Elvis is a man, so Elvis is mortal") as having an unstated premiss - the major premiss (e.g., "All men are mortal"). They are said to be such because these syllogisms become formally valid when the major premiss is added (i.e., it is a gap-filler). I argue that unstated major premises are not gap-fillers: they support a part (...) of the argument that is already given implicitly - the inference claim ("If the premisses are true then the conclusion is true"). As such, their logical status is the same as that of an unstated proposition that supports the minor premiss, which is not part of the argument. Therefore, the so-called "major premiss" is not an unstated premiss of the enthymeme. (shrink)