A detachable burden easily shifted to the shoulders of God, Fate, Fortune, Luck or one's neighbor. In the days of astrology it was customary to unload it upon a star. Alas, things ain't what we should see If Eve had let that apple be; And many a feller which had ought To set with monarchses of thought, Or play some rosy little game With battle-chaps on fields of fame, Is downed by his unlucky star And hollers: "Peanuts! -- here you are!" "The Sturdy Beggar"
The notion of describing problem space entities in terms of responsibilities is one of the core characteristics of OO development. The notion that publicly an entity is only responsible for knowing or doing something introduces a level of conceptual indirection that is important to OO encapsulation, implementation hiding, and DbC. It allows the "client" collaborating with an object to be protected from knowing anything about the details of how the "service" object actually fulfills its contract. (See category on what OO is all about.)