When the United States invaded Iraq in 2003, many public school teachers were forbidden to discuss the war in their classrooms. Such a restriction on free discussion seems outrageous in a liberal democracy. But, although free debate is rarely so directly forbidden, the suppression of discussion and critical thinking in our educational system is widespread. Usually it is accomplished by defining the curriculum so narrowly and specifically that genuinely controversial issues simply do not arise. Without controversial issues, critical thinking is nonexistent or, at best, weak. Students are encouraged now and then to exercise a bit of critical thinking in science or mathematics as they try to solve word problems or think of alternative hypotheses, but such exercises are usually constrained tightly by the topic at hand and the limited knowledge of young students. Further, this sort of critical thinking does not challenge deeply held beliefs or ways of life.