There is no such thing as 'subject matter' in the abstract. 'Subject matter' exists in the minds of perceivers. And what each one thinks it is, is what it is. We have been acting in schools as if knowledge lies outside the learner, which is why we have the kinds of curricula, syllabi, and texts we have. But knowledge... is what we know AFTER we have learned. It is an outcome of perception and is as unique and subjective as any other perception.