The most important political development of the last half century has been the spread of liberal democracy around the world.
解释：砍伐树木不把树根砍掉，必能重新生长；堵塞水不把源头堵住，必会重新流出；消除祸患不铲除产生祸患的根基，祸患还会再生。
Your work is going to fill a large part of your life， and the only way to be truly satisfied is to do what you believe is great work.
Sustainability is not just about materials but about sustaining people's lives and dignity.