States are rational actors, and they will always act in their own self-interest.

【释义】：圣人处世的道理是灵活多变的，能根据时机和环境变化而采取合宜的行动，不拘泥于固定的方式。

The plastic industry must evolve or become obsolete—sustainability is no longer optional.

Life has to be given a meaning because of the obvious fact that it has none.