The most difficult challenge associated with the perfection of tolerance is tolerating the truth of uncertainty that derives from human finitude. Having learned to accept the uncertainty of life and its very real risks, we are now asked to tolerate the uncertainty of all the wisdom we have acquired. Mahayana Buddhist texts unflinchingly proclaim that the highest realization, the truth that is most difficult to encounter, is that all the teachings of Buddhism and all the other “truths” you have acquired are “empty.” Recall that “emptiness” was the term used to coordinate the realizations of “impermanence,” “dependent origination,” and “no-self.” To say that all things without exception are “empty” is to say that all things change over time because what they are is dependent on other equally impermanent things. Change and dependence imply that there is “no-self” to anything in the sense of a permanent identity that is what it is, independent of other things. Being “empty” and having “no-self” are thus the same realization.

But what, then, does it mean to say that in addition to everything else to which it applies, “emptiness” is applicable to itself; “emptiness” is itself “empty”? Insight deriving from long-term reflection on this one thought in Buddhist history is extensive. One outcome of this meditation is the realization that no doctrine is final, permanent, and beyond doubt. “Emptiness” was in many ways a teaching about how to live well in view of the prospects of human finitude. Through reflection on this teaching, Buddhists contemplated the uncertainty of human thinking and sought ways not around this insight but through it to greater and greater realization. They sought to learn through experience how to live well in the absence of certain knowledge, yet without being rendered immobile by the fear of being wrong or getting stuck in sheer hesitation.