Why did Martin Buber call God the Eternal Thou?

Martin Buber referred to God as the "Eternal Thou" to emphasize that the relationship between humanity and God is the purest and most fundamental form of the I-Thou encounter.1

In Buber’s philosophy, an I-Thou relation is a direct, mutual meeting between beings that involves the "fullness of one's being," as opposed to an I-It relation, where the other is treated as an object to be analyzed, used, or manipulated. While human-to-human relationships often lapse into the I-It mode, Buber maintained that the relation with God must always be an I-Thou one.12

By calling God the Eternal Thou, Buber highlighted that God is never an object of thought, dogma, or fixed rules, but a presence to be truly met and addressed. This relationship serves as the model that makes all other genuine I-Thou encounters possible.21