Sid is a failure at what he aspires to be, a poet, and barely is able to hold onto a professorship. In short, these characters are as flawed as we are. And so, by circuitous and unpredictable routes, we converge toward mid-continent and meet in Madison, and are at once drawn together, braided and plaited into a friendship. It is a relationship that has no formal shape, there are no rules or obligations or bonds as in marriage or the family, it is held together by neither law nor property nor blood, there is no glue in it but mutual liking. It is therefore rare.
Friendship is like that.
In fact, if you have a reason for wanting to make someone a friend, you have an agenda, you are pursuing your selfish ends, and sooner or later that will sabotage the relationship anyway. As Frederick Buechner writes, Basically your friends are not your friends for any particular reason. They are your friends for no particular reason. Even if you talk about them, they are beside the point. Stripped, humanly speaking, to the bare essentials, you are yourselves the point.