12 Teaching Minds hypotheses in plumbing as well as in medicine and that these expla- nations exist for repairing a faulty engine and for understanding who committed a crime. It is all scientific reasoning. The difference between plumbing and medicine is in the complex- ity of the science. Not a lot of invention goes on in plumbing and there aren’t all that many explanations to choose from. The degree of difficulty in understanding what is going on and why is what sepa- rates those fields and makes one science and one not. But the basic thought processes are the same. This is important to notice because all these areas of inquiry are what we might call diagnostic. So, and this is the important part, the real issue from a cognitive science point of view is not in teaching science per se, but in teaching scientific activities, one of which is diagnosis. And, since diagnosis is a similar process no matter what you are diagnosing, it makes sense that all through school, diagnosis would be a subject, and not physics or literature. The things that children are asked to diagnose might start with things little kids like, like finding out what is wrong with their pets or their toys, and then move on to things bigger kids like, like cars and crime, and then move on to large issues, like why a business has failed or why our foreign policy doesn’t work. Diagnosis matters a great deal in our lives, yet it is not a subject in school. This is not surprising because the origins of the school subject areas, as I have said, are scholarly. But if we want to teach children to do things that matter and we want to retain their interest because they know intrinsically that these things do matter, then we must have them practice diagnosis all through their school lives, in a variety of venues that correlate with their interests. They don’t all have to diag- nose the same stuff. It is the diagnostic process itself that matters, not what is diagnosed. I have been using the word subject