我们不仅生活在思想的世界中，而且也生活在物质的世界中。
Not only do we live in the world of thought， but also in the world of matter.
The only limit to our realization of tomorrow will be our doubts of today.
The deepest theorems often have the simplest proofs - if you look at them from the right angle.
"The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion."