Michael John Scriven

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.

Part of logic consists in uncovering ways in which logical processes of great universality and utility are over-extended, e.g., in the misguided search for the cause of everything. It is suggested here that the search for missing premises defined as premises that make a deduction out of every argument has its own limits of sense. While often useful, it is sometimes just wrongly used by requiring that the reconstructed argument have the same categorical conclusion as the original one; and sometimes inappropriately used when the argument itself does not rest upon assumptions different from itself

Fallacies are the ‘ideal types of improper inference’, named only because they represent a common or seductive error. Naming them facilitates identification (reducing ‘false negatives’ in argument evaluation), but increases the risk of false positives; it is essentially a cost-effectiveness issue whether to introduce a new name. Statistical fallacies include errors of elementary experimental design, but also conceptual confusions, e.g. of cause with correlation, of association with guilt, where an illicit substitution is made. The focus here is on recent nationwide efforts to replace criteria of merit with correlates of success, in the evaluation of teaching. This involves a number of mistakes, including ‘precipitate decision’, confusing the normative with the descriptive, and using minimax when optimizing or maximin is appropriate, as well as various legal and ethical blunders