4. In each of these groups the simplest facts relate to particular objects, particular acts, thoughts, feelings.
5. Collective facts, facts relating to social groups, to institutions, to general causes that act in history, much more difficult.
a. How represent a wave of prosperity? a panic? a revolution? society itself?
b. Such expressions made intelligible by resolving them, so far as possible, into their concrete elements.
b. The kinds of facts enumerated common to literary, didactic, and scientific history.
c. Degree of difficulty presented by a given type of facts not essentially different for different kinds of history.
d. A principle of grading thus suggested as applicable to one kind of history as to another.
1. Any facts readily visualized possible material for school history.
2. Clear visualization a factor in stimulating interest.
3. Clear visualization of the man, the act, the situation, a necessary key to his mental states.