Buber rejected the label of "philosopher" or "theologian", claiming he was not interested in ideas, only personal experience, and could not discuss God, but only relationships to God.
He explained this philosophy using the word pairs of Ich-Du and Ich-Es to categorize the modes of consciousness, interaction, and being through which an individual engages with other individuals, inanimate objects, and all reality in general.
The concept of communication, particularly language-oriented communication, is used both in describing dialogue/monologue through metaphors and expressing the interpersonal nature of human existence.
Ich‑Du ("I‑Thou" or "I‑You") is a relationship that stresses the mutual, holistic existence of two beings. It is a concrete encounter, because these beings meet one another in their authentic existence, without any qualification or objectification of one another.
Even imagination and ideas do not play a role in this relation. In an I–Thou encounter, infinity and universality are made actual (rather than being merely concepts).
Buber argued that this is the only way in which it is possible to interact with God, and that an Ich‑Du relationship with anything or anyone connects in some way with the eternal relation to God.
the God Buber describes is completely devoid of qualities, this I–Thou relationship lasts as long as the individual wills it. When the individual finally returns to the I‑It way of relating, this acts as a barrier to deeper relationship and community.
The Ich-Es ("I‑It") relationship is nearly the opposite of Ich‑Du.Whereas in Ich‑Du the two beings encounter one another, in an Ich‑Es relationship the beings do not actually meet.