Give the pupils something to do, not something to learn; and the doing is of such a nature as to demand thinking; learning naturally results.

"Every mental state is transitional."

有一个快乐的境况出现，但就有一个不快乐的境况相对立；有一处优美的风景出现，但就立即有一处不优美的风景相抵销。

The true cost of energy must account for both its production and its legacy.

"The aim of life is self-development. To realize one's nature perfectly—that is what each of us is here for."