Why would misunderstanding the relationship of skills and knowledge lead to trouble? If you believe that skills and knowledge are separate, you are likely to draw two incorrect conclusions. First, because content is readily available in many locations but thinking skills reside in the learner's brain, it would seem clear that if we must choose between them, skills are essential, whereas content is merely desirable. Second, if skills are independent of content, we could reasonably conclude that we can develop these skills through the use of any content. For example, if students can learn how to think critically about science in the context of any scientific material, a teacher should select content that will engage students (for instance, the chemistry of candy), even if that content is not central to the field. But all content is not equally important to mathematics, or to science, or to literature. To think critically, students need the knowledge that is central to the domain.