Friendship arises out of mere Companionship when two or more of the companions discover that they have in common some insight or even taste which the others do not share and which, till that moment, each believed to be his own unique treasure (or burden).He also says this:
The companionship on which Friendship supervenes will not often be a bodily one like hunting or fighting. It may be a common religion, common studies, a common profession, even a common recreation. All who share it will be our companions; but one or two or three who share something more will be our Friends.St. Augustine also wrote on the same subject. Augustine reflects on the desire to share a common love, particularly a love for the life of the mind (although that's not what he calls it) has on him. He writes wistfully about it:
In this kind of love, as Emerson said, Do you love me? means Do you see the same truth? - Or at least, 'Do you care about the same truth?' The man who agrees with us that some question, little regarded by others, is of great importance can be our Friend. He need not agree with us about the answer.
...I do love wisdom alone and for its own sake, and it is on account of wisdom that I want to have, or fear to be without, other things such as life, tranquility and my friends. What limit can their be to my love of that Beauty, in which I do not only not begrudge it to others, but I even look for many who will long for it with me, sigh for it with me, possess it with me, enjoy it with me. They will be all the dearer to me the more we share that love in common.Lewis and Augustine have something important to teach us about friendship. Two people can be companions for awhile even if they don't share much in common, but they'll only develop a true friendship if they both love some of the same things. For Augustine the chief of these loves is the love of wisdom, and surely the love of wisdom encompasses the love of truth.
That love has been largely lost in our post-modern age during which a lot of people seem to believe whatever suits their political or religious preferences. So far from loving truth (and wisdom) many seem almost to despise it as irrelevant if it gets in the way of their appetites and prejudices.
I wonder how many modern friendships are grounded in the same love that Augustine muses upon, or even could be.