Taoist roots

From Zen and Japanese Culture, D.T. Suzuki

A monk asked T'ou-tzu, a Zen master of the T'ang period: "I understand that all sounds are the voice of the Buddha. Is this right?" The master said, "that is right." The monk then proceeded: "Would not the master please sop making the sound of a fermenting mass of filth?" The master thereupon struck the monk.

The monk further asked T'ou-tzu: "Am I in the right when I understand the Buddha as asserting that all talk, however trivial or derogatory, belongs to the ultimate truth?" The master say, "Yes, you are in the right." The monk went on, "May I then call you a donkey?" The master thereupon struck him.

Suzuki explains that this monk is engaging in verbalism that leads to complication. The master's blows are meant to awaken the monk from his sleep of logic to realize the "One in All and All in One" nonconceptually.

The image of a fermenting pile of filth suggests a passage in the Zhuangzi where the Master is asked about the nature of the Tao. His response is essentially that it is so all-pervading that it is even in excrement (though using somewhat more direct language).