Some friendly relationships can be kept on argument and discussion, but it is usual for close friends to have similar ideas and beliefs, to have attitudes and interests in common-they often talk about "being on the same wavelength". It generally takes time to reach this point. And the more intimately involved people become, the more they rely on one another. People want to do friends favours and hate to break a promise. Equally, friends have to learn to put up with annoying habits and to tolerate differences of opinion.

In contrast with marriage, there are no friendship ceremonies to strengthen the association between two people. But the supporting and understanding of each other that results from shared experiences and emotions does seem to create a powerful bond, which can overcome differences in background, and break down barriers of age, class or race.