Any life, no matter how long or complex it may be, is made up essentially of a single moment—the moment in which a man finds out, once and for all, who he is.

The line distills a recurring Borgesian preoccupation: that identity is not the sum of accumulated events but a sudden, decisive revelation. It suggests that biography—however sprawling—can be reduced to an instant of self-recognition in which a person apprehends their essential nature, limits, or destiny. The emphasis on “once and for all” frames this as irreversible knowledge: after the moment of recognition, one’s life is retrospectively reorganized around it, as if everything before were preparation and everything after were consequence. In Borges’s universe of mirrors, doubles, and labyrinths, such a moment can be both clarifying and unsettling, because to “know who one is” may also mean confronting the self as a constructed narrative.