反过来，始终反过来：把情况或问题颠倒过来，从反面看。
Invert, always invert: Turn a situation or problem upside down. Look at it backward.
"In observational studies, we often have to rely on assumptions that are not directly testable."
The beauty of a mathematical proof lies in its simplicity and inevitability.
没有内心生活的人是他周围环境的奴隶。
我们是不出现在报纸上的人。我们生活在印刷品边缘的空白处。