Aristotle famously defined human beings as "rational animals." With this, humanity was easily distinguished from the rest of the animal world. Within the history of western thought, it also helped forge certain allegiences. When Christian writers wanted to illustrate the uniqueness of humanity, the rational facility became associated with the concept of soul. (St. Thomas is largely credited with reintroducing Aristole as a respectable presence within the western academy.) Indeed, the German word 'Geist' means both Mind and Spirit!
There is however an arbitariness with such a defination. We can understand human beings in many different ways. One can, for instance, see the capacity of intimacy that human beings display as something distinguishable by degree. True, we can see the capacity for intimacy with Elephants and Dolphens. Yet, such intimacy is expressed physically. In human beings, it can be displayed in a manifold manner.
Before getting ahead of ourselves it is worth reflecting upon what we mean by this word. First, intimacy is generally understood to imply closeness. This is easy enough understood when discribing the kind of physical proximity between lovers. We can also be intimate with friends in a non-sexual way. We may share our concerns with a friend, confiding desires, hopes, diasappointments etc. We still may be considered close to such a friend but this 'closeness' is understood by way of analogy. Second, there comes with this intimacy, whether physical or intellectual, a measure of trust. We choose those people who we wish to be intimate with. As individuals, we do not always allow the public complete excess to our body and soul. Sometimes, we have learnt not to trust certain thoughts and feelings through bitter experience. The friend who laughs when a desire is expressed can quickly become a stranger. Such pain can also help build a wall around that which we consider most sacred.
Already we can see how different this is to the notion that human beings are 'rational animals'. Rationality is something non-personal, objective and open to public view. Intimacy, on the otherhand, is something different from the public persona, something beyond dialogues of Truth and Falsehood. It is for this reason that intimacy can have such an subversive effect.
When one thinks of Romeo and Juliette, we see the lovers rebelling against the wishes of two waring families. In George Orwell's 1984, Winston Smith tries to get beyond the eyes of Big Brother, seeking privacy in order to become intimate with a secret lover. Such intimacy is an act of contrariness, a subversive action beyond the control of the offical dialogues of history, state, meaning and purpose. The desire to become intimate is something entirely human but not in the Aristotlian sense.