In I and Thou, Buber introduced his thesis on human existence. Inspired partly by Feuerbach's concept of ego in The Essence of Christianity and Kierkegaard's "Single One", Buber worked upon the premise of existence as encounter. 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. Philosophically, these word pairs express complex ideas about modes of being - particularly how a person exists and actualizes that existence (see existentialism). As Buber argues in I and Thou, a person is at all times engaged with the world in one of these modes.

The generic motif Buber employs to describe the dual modes of being is one of dialogue (Ich-Du) and monologue (Ich-Es). 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

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 stressed that an Ich-Du relationship lacks any composition (e.g. structure) and communicates no content (e.g. information). Despite the fact that Ich-Du cannot be proven to happen as an event (e.g. it cannot be measured), Buber stressed that it is real and perceivable. A variety of examples are used to illustrate Ich-Du relationships in daily life - two lovers, an observer and a cat, the author and a tree, and two strangers on a train. Common English words used to describe the Ich-Du relationship include encounter, meeting, dialogue, mutuality, and exchange.

[...]

Ich-Es

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. Instead, the "I" confronts and qualifies an idea, or conceptualization, of the being in its presence and treats that being as an object. All such objects are considered merely mental representations, created and sustained by the individual mind. This is based partly on Kant's theory of phenomenon, in that these objects reside in the cognitive agent's mind, existing only as thoughts. Therefore, the Ich-Es relationship is in fact a relationship with oneself; it is not a dialogue, but a monologue.

In the Ich-Es relationship, an individual treats other things, people, etc., as objects to be used and experienced. Essentially, this form of objectivity relates to the world in terms of the self - how an object can serve the individual's interest.

Buber argued that human life consists of an oscillation between Ich-Du and Ich-Es, and that in fact Ich-Du experiences are rather few and far between. In diagnosing the various perceived ills of modernity (e.g. isolation, dehumanization, etc.), Buber believed that the expansion of a purely analytic, material view of existence was at heart an advocation of Ich-Es relations - even between human beings. Buber argued that this paradigm devalued not only existents, but the meaning of all existence.

Empathy- or feeling that the other is not to be categorized into a rigid inductive schema but is simply expressing herself in a certain way at a given moment- is difficult in the real world, all the more so in the surrogate world of internet.