While rummaging among old papers I chanced on a battered typewritten piece, probably belonging to my father (I recognised his handwriting in the corrections that were added to the text). It was a discourse on friendship which he might have copied, in translation, for reasons known to him alone, from one of the ancient philosophers who wrote on friendship. I tried to make out who it could have been, but it was hard, there was no frame of reference. There was a passage that struck me, in which the author claimed that no friendship was possible between a man and a woman because friendship is based on a physiological affinity and among people of different sex the physiological element gives rise to fusions or clashes which are typical of love. If you recognise the argument, please let me know.
My view is that only an ancient philosopher would have written that, for friendship in the ancient world was something that pertained to men and men alone. Also 'physiological affinities' strikes me as being connected to the theory of body humors, which is associated with Hippocrates.
As I said, I could not identify the source but this reflection on friendship sent me straight to the great writings on friendship by Plato and Aristotle. Let's deal immediately with the elephant in the room: in the ancient world, women had virtually no status, thus these discussions of friendship are about men. This, however, does not mean that we should dismiss the writings of these philosophers, for indeed there is much we can derive by mining the ancients and applying their thinking to our contemporary world, with due changes.
Friendship is a slippery concept in the day and age of social media friends, who could not be further from the φιλοι of the time of Plato and Aristotle. Friendship ( or φιλια) is discussed by Plato in the Lysis . Friendship and love have much in common, says Plato, but then in the dialogue Socrates (Plato often discusses his ideas using Socrates as his main character and narrator) raises the fiollowing points:Friendship occurs between people who are similar, interpreted by Socrates as friendship between good men.
Friendship may arise between men who are dissimilar.
Friendship arises between men who are neither good nor bad and good men.
Friendship arises between those who are related (οἰκεῖοι "not kindred") by the nature of their souls.