Teaching students to think critically is more about imparting a set of skills and habits than about teaching bits of theory. In developing this textbook, I tried to incorporate several features that I thought would make teaching critical thinking both easier and more effective.
Most significantly, I steered clear of any formal notation aside from the very simplest. It is not that I doubt the value of learning formal logic. In fact, I think that many students thrive while studying it. But in my experience there is so much that most students need to learn before they can see the value of mastering a formal system, and so much more benefit they can derive from a non-formal approach to critical thinking. Instead, I tried to think of this text as like an introduction to practical or applied epistemology: offering systematic advice, and lots of practice, on the best way to go about deciding what to believe and what to do.
It is worth noting here that I treat what is sometimes called enumerative induction as a form of reasoning by analogy. It seems to me that using samples to draw a conclusion about an entire group or population just is reasoning by analogy, and that it can be usefully taught as such. I also say, and this perhaps is more controversial, that reasoning by analogy can be valid. Of course, I do not mean that it is formally valid in the way that modus ponens is formally valid. Reasoning is valid when it is not possible for the premises to be true and the conclusion to be false. The fact that some reasoning can be known to be valid just from its form alone is, of course, important, and I discuss some of these forms in chapters 5 and 6. But it is important to keep in mind that not all valid arguments are formally valid, (e.g., The table is blue, therefore it is colored), and not all arguments that are formally invalid are really invalid (e.g., If Jones is a male, then he is a bachelor; Jones is a bachelor; so, Jones is a male.) Judgment is always needed, it seems to me, in assessing the strength of a piece of reasoning, and this judgment is better taught by focusing on the idea of validity itself. I also think that what I say in Chapter 6 makes a reasonable and pedagogically responsible case for my view that reasoning by analogy can be valid.
I had originally planned to dedicate a chapter to thinking critically about what to do. But I worried that much of it would simply repeat points that had been made earlier and, in so doing, would make deciding what to do seem like a lesser cousin to deciding what to believe. As I worked (and then re-worked) the first 6 chapters, it seemed to me that I could elegantly discuss deciding what to do as we went along, when the topic at hand seemed relevant. I have thus included several “boxes” discussing various aspects of deciding what to do.
The book includes several other kinds of boxes as well. Some identify important mistakes that a good critical thinker ought to avoid. Some provide summaries of the discussion in the body of the text. Some offer examples of critical thinking across the curriculum. Some offer practical tips and rules of thumb. All are intended to make the text more readable and the concepts and skills more accessible.
I also decided that rather than dedicate a chapter to informal fallacies, I would discuss them in what struck me as their proper context. It seems to me that there is no easy way to organize the different kinds of mistakes into a small number of categories without distorting their differences or exaggerating their similarities. Some of the mistakes have to do with clarifying meaning; others with ascribing views to others; some with assessing evidence; others with assessing validity. Several mistakes can occur at several otherwise quite distinct stages in deciding what to do or to believe. Rather than try to force the various mistakes into artificial categories, it seemed to me better to discuss them as we went along. For easy reference, though, I have collected them all in an appendix at the end of the book.
Careful training and repeated practice are crucial to learning any skill, and critical thinking is no exception. I have tried to include a large and varied collection of exercises. But I strongly encourage you to bring your own exercises to class and to encourage your students to seek out arguments and reasoning to share during the class time. In my experience, students learn far more when they are required during class time to participate in the construction, analysis, and assessment of examples of reasoning about what to do or believe. I have included, at the end of most of the chapters, exercises that are specially designed to help students transfer the concepts and skills they are learning to other corners of their lives. My thought is simply that there is little point in teaching someone to think critically if they see no place for it at home, in their own discipline, or at work. Over the years I have experimented with all of these exercises, making adjustments as I went along. The exercises are in a form that I find to be both effective and not overly intrusive. But I encourage you to adjust, alter, add, subtract, and modify as you see fit. The important thing is to find ways to help students see that they are learning skills and concepts that have application and value after the final exam.