Be happy, but never satisfied.
生活要快乐,但绝不要安于现状。
数学不是沿着一条清理得很好的高速公路小心行进,而是一次进入陌生荒野的旅程,探险者常常会迷路。
No testimony is sufficient to establish a miracle unless the testimony be of such a kind that its falsehood would be more miraculous than the fact which it endeavors to establish.