世間萬物有不同的相貌，難易、長短、高低、前後、美醜。當我們認定某些事物為「美」時，心中就出現了標準，將某些事物定為「不美」，無法分別出事物的常態；或是當我們認為事情已經成功時，就會結束奮鬥的狀態，無法保持平常心。只有讓事物保持原來的狀態，不下任何評斷，才能真正與萬物同在。這是老子《道德經》中所建議如何看透世事的一個原則。

中文所謂的「相」除了有「互相（mutual）」之意，也有所謂的「世間萬相、相貌（appearance）」之意。

老子《道德經》〈道經〉第二章

天下皆知美之為美，斯惡已；
皆知善之為善，斯不善已。

有無相生，
難易相成，
長短相形，
高下相盈，
音聲相和，
前後相隨。

是以聖人處無為之事，行不言之教；
萬物作而弗始，
生而弗有，
為而弗恃，
功成而不居。
夫唯弗居，是以不去。

Chapter 2, Tao Te Ching

As all is aware of making things beautiful, thus perceived the ugly;
As all is aware of being good at things, thus perceived the bad.

"With" and "without" produce each other (or the appearance);
"Hard" and "easy" accomplish each other (or the appearance);
"Long" and "short" figure each other (or the appearance);
"High" and "low" fill each other (or the appearance);
"Tone" and "sound" compose each other (or the appearance);
"Before" and "behind" vary each other (or the appearance).

Therefore a Sage is involved with inaction, and conducts no speech;
Mutitudinousness rises without origination,
Bears without ownership,
Does without claim,
And complishes without reliance.
For only without reliance, the Sage hasn't to dismiss anything.