看着容易，要学会就很难；千万不要把容易得到的东西看得普通，就不知道珍惜。

The past is not behind us; it is within us.

We are communal histories, communal books. We are not owned or monogamous in our taste or experience.

译文：学习贵在实践，而非空知;贵在有用于世，而非无用之学。反对空谈，提倡经世致用。