What Lao-tzu said "is hidden but always present"

I believe the answer is:

(Other definitions for tao that I've seen before include "true path" , "Philosophical principle, the way" , "Source of existence (Chinese)" , "religious way" , "path of Chinese" .)

I've seen this clue in The New York Times.

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What Lao-tzu said "is hidden but always present" (3)