After Affection, Lewis tells us, in The Four Loves, of the second category of love–Friendship.
For then it will seem to us that we – the four or five – have chosen one another, the insight of each finding the intrinsic beauty of the rest, like to like, a voluntary nobility; that we have ascended above the rest of mankind by our native powers. The other loves do not invite the same illusion. Affection obviously requires kinships or at least proximities which never depended on our choice. And as for Eros, half the love songs and half the love poems in the world will tell you that the Beloved is your fate or destiny, no more your choice than a thunderbolt, for “it is not in our to love or hate.” Cupid’s archery, genes – anything but ourselves. But in friendship, being free of all that, we think we have chosen our peers. In reality, a few years’ difference in the dates of our births, a few more miles between certain houses, the choice of one university instead of another , posting to different regiments, the accident of a topic being raised or not raised at a first meeting–any of these chances might have kept us apart. But, for a Christian, there are, strictly speaking, no chances. A secret Master of the Ceremonies has been at work. Christ, who said to the disciples, “Ye have not chosen me, but I have chosen you,” can truly say to every group of Christian friends “You have not chosen one another but I have chosen you for one another.” The Friendship is not a reward for our discrimination and good taste in finding one another out. It is the instrument by which God reveals to each the beauties of all the others. They are no greater than the beauties of a thousand other men; by Friendship God opens our eyes to them. They are, like all beauties, derived from Him, and then, in a good Friendship, increased by Him though the Friendship itself, so that it is His instrument for creating as well as for revealing. (p. 189)
One needs to point out the volitional aspect of friendship, in contrast to Affection and Eros. We choose our friends more so than we choose who we work with, or even who we love (don’t we just fall in love)–nevertheless, usually an erotic love started out in friendship. It is strange to think about the will in deciding friends and reconcile it with Divine Providence. How does my free will in choosing friends relate to God’s plan in my having friends?