1. The best way to learn is to do. From an article by Paul Halmos about teaching math. I began self-experimentation to learn how to do experiments.
2. Everyone’s different. My theory of human evolution says we changed in many ways to facilitate trading. (For example, language began as advertising.) The more diverse the expertise within a group, the more members of the group can benefit from trade. Following this logic, mechanisms evolved to increase diversity of expertise among people living in the same place with the same genes. (For example, a mechanism that causes procrastination.) The theory implies that there is something inside every student that pushes them toward expertise they want to learn but they are being pushed in many different directions what they want to learn varies greatly. If you accommodate the latter (diversity in what students want to learn), you can take advantage of the former (an inner drive to learn).
The novelty is #2 the idea that #2 is relevant to teaching. Human nature: People who are the same want to be different. Formal education: People who are different should be the same. At Berkeley, most professors appeared to have little idea of the diversity of their students. (At least I didn’t, until I gave assignments that revealed it.) Almost all classes treated all students in a class the same: same lectures, same assignments, same tests, same grading scheme. I heard dozens of talks about how to teach. Supporting or encouraging individuality never came up. Now and then I told other professors these ideas at a party, for example. “Everyone’s different, but our classes treat everyone the same,” I’d say. No one agreed. It was a new and apparently distasteful idea. Too much work was one response.