Among all God's creatures, only human beings and a few other large mammals are capable of recognizing their own reflection in a mirror. Psychologists regard mirror self-recognition as a key step in developing a concept of self. However, the emergence of self-awareness may blind us to a deeper identification with others. We all have a little bit of the narcissist in us. A narcissist is generally thought of as a person who falls in love with his own reflection. However, the original Narcissus of Greek mythology was under a spell that prevented him from recognizing that the object of his affections was himself. Clinical narcissists are unable to see past their own reflection to recognize the independent existence of others. The paradox is that we must be able to appreciate that others have an identity distinct from our own before we can arrive at a deeper recognition that each is the other.
The ethical teaching to love one's neighbor as oneself is found in both the Old and New Testaments. Variations on the Golden Rule ("Do unto others..."), which proceeds from the same premise, are found in every major religious tradition. However, one needs only a cursory understanding of human affairs to realize these admonitions are mostly honored in the breech, if at all. It often seems people are nice to each other only when they perceive it to be in their self interest to do so. If nothing else, this demonstrates that we don't truly understand what our self interest is.
When Jesus said, "You shall love your neighbor as yourself," he had more in mind than just being nice to each other. In effect, he was saying you must love your neighbor as yourself because your neighbor is yourself. We are more than just brothers or sisters under the skin; we are all part of the same being. This doesn't mean that my neighbor and I always think alike or that what is good for me is necessarily also good for my neighbor. But at the deepest level, there is a mutuality of interest that should make me think twice before pursuing my own self-interest at the expense of others. It is a mark of self-awareness to be able to look into a mirror and recognize one's own image; it is a mark of higher awareness that one can look into the face of another and also recognize oneself.