I-Thou is a relationship in which the other is not separated by discrete bounds. Nondualism.
"After absolute encounter we come to see every other being (nature, animals, people) as a You. We come to feel affection for everyone and everything, and to have a sense of loving responsibility for the whole course of the world. This transformation, Buber tells us, is divine revelation." - SparkNotes: I and Thou: Summary
I and Thou relates to Tat Tvam Asi.
The meaning of this saying is that the Self - in its original, pure, primordial state - is wholly or partially identifiable or identical with the Ultimate Reality that is the ground and origin of all phenomena.
It also relates to "Waḥdat al-Wujūd" (Unity of Existence) in Sufi metaphysics.
Joanna Overing on the Self in Piaroa society:
"The Piaroa view is radically externalist: the forces for selfhood have their origin external to the self, and as such have significance in the wider cosmic order.
Such a view is in contrast with the Western notion of the self, which is radically interiorised from the start, with consciousness and reason conceived in large part as autochtonous to the mind itself."
Since the advent of postmodernism this Western notion of the self is under siege, according to Rick Roderick. But perhaps we simply have to shift perspectives and aim for I-Thou relations with the world.
Thoughts on Universe of Things: On Speculative Realism, by Steven Shaviro:
Drawing on process philosophy and evolutionary panentheism by Alfred North Whitehead. Video by 0ThouArtThat0.
David Ray Griffin on Panentheism, a Postmodern revalation: