After defining the modes of experience and encounter, Buber turns his energies toward tracing the emergence of the desire for encounter. He claims that it is primary, in the sense that it emerges first in the human psyche. His proof for this claim rests on his two analyses of language emergence: first, he traces the cultural development of man from primitive times to modern, showing that early languages focus on relations rather than on distinctions, and then he analyzes the phenomenology of the human mind as it develops from fetus to adult, showing that we enter the world yearning for relation, and only much later develop an interest in experience.
He begins by looking at the language of primitive peoples, and notes that their words generally refer to relations rather than to isolated objects. For instance, where we say "far away" the Zulu say "Where one cries, 'mother, I am lost'". There is no separation in this language between the object and the subject: place cannot be defined without reference to man's relation to that place. Primitive people, he concludes, do not analyze the world into component parts, but rather experience it in its original unity. They view the world as a unified relationship rather than as a conglomerate of distinct objects.
Buber claims that we see the same early emphasis on relationship in child development. An infant comes into the world yearning to relate. He reaches out his hand even when he wants nothing in return, he stares at walls for long periods on end, and he "talks" when no one else is present. All of these behaviors, Buber claims, are proof that the baby has an overpowering desire to relate. It is not that he sees objects and people and wants to relate to them, but something even stronger: he is longing to relate to anything and everything, and is constantly searching out partners. The newborn has a drive to turn everything into a You. In its initial stage this drive aims exclusively toward tactile contact, then later in widens its scope to include optical contact, and finally it aims at true reciprocity, asking for a response in the form of tenderness.
At this point, the child knows only relation; it does not even have the concept of an I distinct from the "I–You". Only later, as the child realizes that there is a constant in all of its relationships, does the concept of the I emerge. We only receive our idea of the I, then, on this view, through a You; we get our sense of self through relation. Once the child develops the concept of an I, he can begin to experience the world. Once he is conscious of an I he can also become conscious of objects as separate from the I. He can place things in their spatio-temporal context, begin to understand causality, to coordinate, to manipulate, and to know. The need to relate, however, persists.
Buber appeals to child development not only to establish the primacy of relation, but also to trace its origins. Our need to relate, he theorizes, results from the manner in which we enter the world. Prenatal life is a life of ultimate encounter; the womb is the universe for the fetus, and there is a natural reciprocity between fetus and mother. When we emerge into the world from this state of pure relation, we immediately yearn for something to take its place. Instead of a natural association, though, we begin to want a spiritual one. This inner desire is what Buber calls our "innate You" and the "secret image of a wish".
When viewed as analytic arguments, the discussions of human development and of primitive language raise several major worries. Looking first at the argument for the claim that we do in fact have the mode of encounter available to us, a severe flaw is apparent immediately. As an analytic piece of reasoning, the argument would look like this: (1)Human beings have the desire for a spiritual relationship that mirrors the physical relationship of the fetus to its mother. (2) Therefore, human beings can enter into such a relationship.