You and I. Martin Buber
Buber views the relationship between man and God and his fellow man as existential, dialogic, and religious principles.
He presents his thesis on human existence. Inspired by Feuerbach's "The Essence of Christianity" and Kierkegaard's "The One," Buber formulates the premise of existence as encounter. He explained this philosophy using the word pairs Ich-Du (I-Thou dialogue) and Ich-Es (I-It [my inner self] monologue) to classify the modes of consciousness, interaction, and being through which humans interact with other people, inanimate objects, and all of reality. In theology, he associated the former with the Jewish Jesus, and the latter with the Apostle Paul (formerly Saul of Tarsus, a Jew). In philosophy, these word pairs express complex ideas about modes of being—specifically, how humans exist and realize this existence. The author argues that humans constantly interact with the world in one of these modes.
The common motif Buber uses to describe dual modes of existence is dialogue (Ich-Du) and monologue (Ich-Es). The concept of communication, especially linguistic communication, is used both to describe dialogue/monologue through metaphors and to express the interpersonal nature of human existence.