Friendship involves close personal relations, affection, caring for and commitment to another. It is intertwined with other emotions such as love, passion, spiritual love, sexual love, patronage, romance and kinship. Friendship is essentially a kind of relationship grounded in a particular kind of special concern each has for the other.
A necessary condition of friendship, according to most views, is that the friends care about the other for his or her sake. Such caring involves both sympathy and action on the friend's behalf. Friendship differs from other interpersonal relationships, such as relationships among colleagues, because it is a more intimate relationship. To enter into and sustain a friendship one will normally trust considerably his or her friend's goodwill towards him or her.
An important condition of friendship is also shared activity. Friends engage in joint pursuits, which are partly motivated by the friendship itself. Shared activity is important because friends normally have shared interests as part of the intimacy characteristic of friendship as such. Therefore, the shared pursuit of such interests is an important part of friendship. Friendship is valuable because it is instrumentally good. It enhances life and contributes to a flourishing life for both individuals involved in such a relationship.
In ancient Greece and Rome, friendship was the dominant paradigm. Later, in Christian teachings in medieval Europe, human friendship was subordinated to spiritual friendship. The modern period focused on impartiality and relegated friendship to the private sphere. Toward the end of the twentieth century there were renewed discussions about the role of friendship in society and debates about the ethics and politics of friendship. Different eras have emphasized different aspects and interpretations of friendship.
Anthropological evidence shows many examples of the role of friendship in different societies and culture. The Arapesh of northwestern New Guinea, the Hopi of Arizona, and the Tikopia in the Solomons have ritual or ceremonial bonds of non-kin friendship, mainly between men. However, the societies of classical Greece and Rome were the traditions that focused most explicitly on friendship. In most of the classical philosophical writing on friendship, a sociological context of male-male friendship is presupposed.
The ancient canon of friendship stressed the interests of the "other self" and reciprocal consideration, as well as the role of friendship, in contributing to a good and virtuous life. In the medieval period, this canon was superseded by the concept of spiritual friendship. The relationship between man and godhead became prominent amid the rise of Christianity and hieratic religions. Monks and theologians redefined the concepts of love and friendship, including God as an essential mediating force between human friendships.
In most philosophy, poetry and literature, male-female relationships are discussed in terms of romance, passion, sex and marriage, rather than friendship. Some of the ancients acknowledged friendships between men and women but almost exclusively as husband and wife. Courtly love of the Middle Ages as well as the idealized relationships of the Romantic era emphasized the unattainable, idealized and exclusive male-female intimacy rather than equal affectionate friendships. In the 1960s, men and women were friends fighting political battles as women took part in civil rights and antiwar movements. However, the sexual revolution focused not on nonsexual friendships but on carnal relationships.
In discussions about friendship between women, both lesbian and non-lesbian relationships are included. Women's traditional role has been in the home and friendship assumed more importance as kinship ties were stretched or broken as a result of social mobility. In medieval monastic writings, women were often portrayed as a danger to men and the object of inferior emotions such as carnal desire. In the nineteenth century, women expressed their romantic friendships in affectionate letters to each other. At the end of the nineteenth century and the beginning of the twentieth century, the suffragettes interspersed their political communication with expression of personal friendship.
In the twentieth century, friendships between women became civic bonds important for politics. In the 1960s, the second wave of feminism produced a women's network of consciousness-raising groups. Women relied on each other for support.
Towards the end of the twentieth century, movements such as communitarianism, feminism and post-modernism challenged the impartiality of liberalism and the objectivity of modernism. These challenges created a rich scholarly debate and resurrected some of the ideals of classical philosophy in a bid to recognize the valuable role that can be played by friendship in the future.