Since critical thinking requires background knowledge, a further seven chapters were commissioned to provide it, in Part IV, on topics that are widely addressed in critical thinking courses and textbooks.

The web is today the dominant venue for the practice of critical thinking, and Sally Jackson’s timely Chapter 15, offers advice about how someone who thinks critically uses the web—and includes ways to avoid being used by the web. The different forms and purposes of definition are covered in Robert Ennis’s Chapter 16, along with advice about how to select the best kind of definition for your purposes. How to recognize unwarranted generalizations and distinguish them from legitimate ones are laid out in Dale Hample and Yiwen Dai’s Chapter 17. In our everyday thinking we rely on the authority of various alleged sources of belief and knowledge, including experts. Mark Battersby, in Chapter 18, discusses how the critical thinker distinguishes reliable from unreliable authorities: experts and other sources. While logic is not equivalent to critical thinking and while there is little evidence that learning formal logic transfers to critical thinking ability, a number of logical concepts do play key roles in critical thinking—as becomes clear in G. C. Goddu’s essay, Chapter 19, on logic and critical thinking. “Abduction” and “argument to the best explanation” are bandied about as forms of reasoning. John Woods, in Chapter 20, makes crystal clear Peirce’s concept of abduction and its connection to argument from the best explanation. Critical thinking entails evaluation, and evaluation theory pioneer, Michael Scriven, discusses the logic of evaluation in Chapter 21.

The reader whose thinking practices are informed by the contents of these seven chapters will be capable of subtle and complex critical thinking analysis over a wide range of subject matters.