Such experiences are probably rather common in the lives of adolescents, but I didn't begin to understand it fully until I read Plato's Symposium. If you don't remember the conversations in there or if, by some travesty of justice, you've never actually read the Symposium, at 202a Socrates and Diotima are discussing the question whether Love (that is, the god Erôs, though clearly it's meant to be a metaphor for the Platonic concept of Love Itself) is ugly or beautiful, and Diotima introduces the notion of human understanding as a means to elucidate what she has in mind.
"What do you mean, Diotima," I [Socrates] said. "Is love then ugly and evil?"The suggestion that there can be intermediary stages between two extreme manifestations of some property was probably one of Plato's most significant and interesting discoveries. It is something that we take for granted these days, but for the ancient Greeks, at least until Plato came along, it seemed valid to infer that, say, justice is just because it is not unjust. They saw opposed properties as contraries rather than contradictories, and this rather severely limited the scope of their conceptual space.
"Hush," she cried. "Must that be ugly which is not beautiful?"
"Certainly," I said.
"And if something is not wise, it must be ignorant? Do you not see that there is a mean between wisdom and ignorance?"
"And what may that be?" I said.
"Right opinion," she replied, "which, as you know, being incapable of giving a reason is not knowledge (for how can knowledge be devoid of reason?), nor again, ignorance (for neither can ignorance attain the truth), but clearly is something that is a mean between ignorance and wisdom."
"Quite true," I replied.
"Do not then insist," she said, "that what is not beautiful is of necessity ugly, or what is not good, evil; or infer that because, as you agree, Love is not beautiful and good, he is therefore ugly and evil; for he is a mean between them."
In Plato's metaphysics we begin to see an analysis of the scala naturae that attempts to explain (even if in rather metaphorical language) how it is that human understanding progresses from meager beginnings to full comprehension via a series of ever more precise abstractions from the domain of experience. For Plato, this sequence of abstraction is not a process of discovery but of recollection, because he believed that the fundamental objects of knowledge are already familiar, in some sense, to our rational faculty right from birth. It is the very essence of the rational faculty to have knowledge of these fundamental objects (or substances, ousiai), and so in a certain sense every human being desires, by nature, to acquire knowledge in the sense limned by Plato in his epistemology. Although we do have other desires, material as well as intellectual, it is this desire for knowledge that, at least in principle, ought to govern the best sort of human life. On this account, even the love that we feel for other human beings is really nothing more than a material manifestation of the immaterial (or spiritual, if you will) desire of the intellect for knowledge.
Our intellect desires different sorts of knowledge, because knowledge has different sorts of objects. But there is one object of knowledge that, in a sense, surpasses all others in power and dignity: the object of knowledge that is the Form of The Good Itself. Plato illustrates this metaphorically with a story about an ascent of sorts in the objects of love (210ad):
"These are the lesser mysteries of love," Diotima said. "He who would proceed aright in this matter should begin in youth to visit beautiful bodies; and first, if he be guided by his instructor aright, to love one such body only, and in it he should engender beautiful thoughts; and soon he will of himself perceive that the beauty of one body is akin to the beauty of another; and then, if beauty of appearance is his pursuit, how foolish would he be not to recognize that the beauty present in all bodily forms is one and the same! And when he perceives this he will abate his violent love of the one, which he will despise and deem a small thing, and will become a lover of all beautiful bodily forms; in the next stage he will consider that the beauty of the soul is more honorable than the beauty of the body, so that someone even of slight beauty, but virtuous in soul satisfies him, and he loves and cares or him, and brings to birth argument of the kind to improve the young until he is compelled to contemplate and see the beauty of institutions and laws, and to understand that the beauty of them all is one family, and that personal beauty is a trifle; and after laws and institutions he will go on to the sciences, that he may see their beauty, being not servilely in love with the beauty of one youth or man or institution, himself a slave, mean and small-minded, but drawing toward and contemplating the vast sea of beauty, he will create many fair and noble thoughts and notions in boundless love of wisdom; until on that shore he grows and waxes strong, and at last the vision is revealed to him of a single science, which is the science of beauty everywhere.The higher mysteries of love, which Diotima goes on to explicate for Socrates, consist in the study of the Form of Beauty Itself, an eternal and unchanging object of the sort most deeply desired by the soul.
For Plato, then, the physical love that we feel for one another is but a manifestation of a deeper intellectual longing for the Form of the Good. The Christian version of this story holds that the physical love that we feel for one another is an image of the deeper love that we have for God and he for us. It is something that is built into our very nature, that we cannot avoid. It is as automatic as that sense of jitters that I used to get when I saw Cynthia Shook walking down the hall. Of course there is a biological explanation for that, but the materialist who focuses on the physical explanations will necessarily miss the metaphysical truths that make the physical explanations true. My early crush was soon replaced, as is everyone's, by a more mature form of love, and that more mature form was itself replaced by yet another, even more mature form. Eventually I found myself married, with children, feeling ever deeper loves not only for my family and my fellow humans, but for my creator as I made the ascent from mere crush to love of God. It is a journey that never really ends in this lifetime, for our final cause is the Beatific Vision, which will serve as the final step in the ascent.
In a scheme such as this we can see quite easily why love of one's enemies is better than love of one's friends. Even sinners love their friends, but to love one's enemies requires a more profound understanding of what love actually is, a deeper experience with loving and a more complete knowledge of what the proper object of love is. Lent is a rather useful time for experimenting with this, because we are asked to abandon our lusts in favor of loves: by immersing ourselves in prayer, we abandon our lust for time to ourselves in favor of love of God and neighbor; by fasting we abandon our lust for material comfort in favor of love of God and neighbor; by giving alms we abandon our lust for material possessions in favor of, well, God and neighbor. In abandoning these lusts in favor of loves, we learn to experience love, we habituate ourselves and teach our soul-body compounds to prefer the one over the other so that we may continue the ascent more easily, more naturally. Soon we come to see that the distinction between love of God and love of neighbor is not a genuine dichotomy, because there aren't two loves, but One Love. If we make it that far we have a better chance of making it to that state where the One Love is all in all.