Sometimes, the hardest battles are fought within the confines of our own minds.
有时候,最艰难的战斗是在我们自己的脑海中进行的。
The utility of an idea determines its place in mental life.
The mind is nature's instrument for dealing with reality.
煤炭曾是工业进步的支柱,但其未来必须平衡经济需求与环境责任。