... if Peter is prepared to make sacrifices for Paul, so Paul should be prepared to make sacrifices for Peter, or else he is selfish, ungrateful, callous, ruthless, etc.
'Sacrifice' under these circumstances consists in Peter impoverishing himself to do something for Paul. It is the tactic of enforced debt. One way of putting this is that each person invests in the other.
The Politics of Experience and The Bird of Paradise, p.76