Baraka_Guru

It's in the Critique of Pure Reason, under the section Transcendental Doctrine of Elements, "Transcendental Logic" (Analytic of Principles).

Critique of Pure Reason - Wikipedia, the free encyclopedia

I wish you luck reading it, however, as it is understood to be one of the most difficult texts of Western philosophy; its arrangement is quite labyrinthine.

I think the section you want is here:
Critique of Pure Reason (Analytic of Principles)

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Knowing that death is certain and that the time of death is uncertain, what's the most important thing?
—Bhikkhuni Pema Chödrön

Humankind cannot bear very much reality.
—From "Burnt Norton," Four Quartets (1936), T. S. Eliot