One of the first obstacles to studying critical thinking is the perception that the issues it takes up are either trivial or impossible. On one hand, we find simple examples about whether there's a dog in Pat's garage, or whether this brand of toothpaste will promote dental hygiene better than that one. You'd think that anyone old enough to take a course like this can already handle such issues. On the other hand we find debates that come down to questions of what policies a government should pursue, or what makes one action morally preferable to another, or what kinds of experiences the human mind is logically capable of. Most of these come down to questions of value: What makes something good, right, beautiful, just, wise?
The rest of the questions seem to speculate about knowledge beyond any ordinary experience. They have that familiar sound of issues we could argue about forever without arriving at any truth. Set aside the simple cases for now. As you continue to study critical thinking you will find many of them more complex than they first appeared, something like the way simple poems open up to reveal new intricacies when you really study them.
What about the insoluble questions? Why discuss what can't be settled? Why not admit that we have different opinions and leave things there?
At this point it is crucial not to reach for inexpensive skepticism about the equality of all positions. In the first place, adopting a skeptical view like relativism or subjectivism leads not to a different way of thinking about difficult issues, but to not thinking about them at all. When all opinions are equally good we have no need to find reasons for one opinion instead of another. Without the attempt at finding such reasons, all that remain are dogmatic assertions.
Second, the intractability of certain issues is only half of the truth about them. Yes, there are questions that people have always stumbled over, and that no one has settled once and for all. But it's just as true that people have always felt compelled to ask and discuss them. Human beings have this tendency to ask what knowledge is, or whether God exists, or what makes a given action wrong, or what makes art valuable, or what makes some public policies more just than others. To ask such questions is to crave something more than mere opinion: It is to ask whether our opinions are right. Anyone satisfied by the "information" that every answer is as good as every other answer never felt gripped by the question in the first place. Suppose someone says, "I've always thought of democracy as the best form of government. Now I wonder whether I was right." This person will never accept the reply that it all depends on your opinion, because the motive behind the worry was precisely the desire for more than habitual opinion.
If we may identify a single central purpose behind the study of critical thinking, it is the improvement of our ability to go beyond habitual opinion and find good reasons for one side of an issue or another.