“When there is great doubt” says a Zen aphorism that Kusan Sunim kept repeating,”then there is great awakening. This is the key. The depth of any understanding is intimately correlated with the depth of one’s confusion. Great awakening resonates at the same “pitch” as great doubt. So rather than negate such doubt by replacing it with belief, which is the standard religious procedure, Zen encourages you to cultivate doubt until it “coagulates” into a vivid mass of perplexity…
Great doubt is not a purely mental or spiritual state: it reverberates throughout your body and your world. It throws everything into question. In developing doubt, you are told to question “with the marrow of your bones and the pores of your skin.” You are exhorted to “be totally without knowledge and understanding, like a three-year-old child.” To pose a question entails that you do not know something…To ask “What is this?” means you do not know what this is.
To cultivate doubt, therefore, is to value unknowing. To say ” I don’t know” is not an admission of weakness or ignorance, but an act of truthfulness: an honest acceptance of the limits of the human condition when faced with “the great matter of birth and death.” This deep agnosticism is more than the refusal of conventional agnosticism to take a stand on whether God exists or whether the mind survives bodily death. It is the willingness to embrace the fundamental bewilderment of a finite, fallible creature as the basis for leading a life that no longer clings to the superficial consolations of certainty.
~Stephen Batchelor, “Confessions of a Buddhist Atheist“