A law of nature， lex naturalis， is a precept or general rule found out by reason， by which a man is forbidden to do that which is destructive of his life or takes away the means of preserving the same.

世界上充满了神奇的事物，耐心地等待着我们的感官变得更加敏锐。

Maybe every man has had two such women, at least two. Married to a red rose, over time, the red becomes a mosquito blood stain on the wall, while the white remains "moonlight before the bed"; married to a white rose, the white becomes a grain of sticky rice on the clothes, while the red remains a cinnabar mole on the heart.

自然实验可以为经济问题提供有价值的见解。