Friends never cheat on each other, or take advantage, or lie. Friends do not spy on one another, yet they have no secrets. Friends glory in each other's successes and are downcast by the failures. Friends minister to each other, nurse each other. Friends give to each other, worry about each other, stand always ready to help. Perfect friendship is rarely achieved, but at its height it is an ecstasy.

An epic American exploration: the friendship of Lewis and Clark (ed. 1998)