The way in which men produce their means of subsistence depends first of all on the nature of the actual means they find in existence and have to reproduce.

有了一些小成绩就不求上进，这完全不符合我的性格。攀登上一个阶梯，这固然很好，只要还有力气，那就意味着必须再继续前进一步。

应该让材料自己说话。

森林的真正价值不能仅用板英尺来衡量。