Ideas of friendship as developed within philosophy and theology are distinct from, and more demanding than the notion of ‘being friends with someone’ that has developed in recent times, especially since the invention of social media. In terms of the latter a ’friend’ may be a mere acquaintance with whom one shares some interest, or a person with which one has (or hopes for) a mutual liking. This loose notion allows for the possibility of having a very large number of ‘friends’ and that is something sought for as a mark of one’s popularity. By contrast, ‘friendship’ as it has featured in the thought of major figures such as Plato, Aristotle, Augustine, Aquinas, Erasmus, and Hegel is something necessarily restricted. For Plato, ‘friends’ have a depth of knowledge and interest in one another’s moral qualities, while Aristotle distinguishes three kinds of friendship: those grounded in 1) enjoyment of the other, 2) usefulness to one another, and 3) admiration and affection for the virtues of the other. While these kinds of interest differentiate the forms of friendship, they all involve some degree of concern for the good of the friend, hence they are not simply self-satisfying. With Christianity the Greek idea of friendship (philia) as responsive to features of the other, begins to blend with that of love (agape) for another that does not depend upon them satisfying some condition such as being pleasing, or useful. The love of a parent for a child is the most obvious form of this and it is significant that Jesus refers to the Divine love for human beings as being ‘fatherly’. Human love of God is a complex notion combining admiration, gratitude and affection. Likewise, the idea of friendship with God has to be reconciled with the fact of the radical existential and qualitative asymmetry between creature and creator. Nonetheless, this is a theme in spiritual writings of a mystical sort, though again it is significant that its divine partner tends to be the Son who, through the incarnation, took on human nature, rather than the Father or the Holy Spirit.