For 10 points, name these places in modal logic which do not necessarily exist.
Robert Adams made a moral argument against the existence of these entities, as they make us powerless to do anything that would improve a situation. Another thinker attacked "ersatzist" theories of them in a book that distanced itself from the view of these as maximally consistent sets of propositions. These things are related to one another through accessibility relations, and a set of them with a set of accessibility relations forms a (*) frame. Counterpart theory holds objects can only exist in one of these; that theory was developed by David Lewis in his book "on the plurality" of these entities. Saul Kripke criticized treating these as "distant planets" we view dimly through a telescope and introduced the phrase "rigid designator" to define objects which are the same in all of these entities the objects inhabit. For 10 points, name these places in modal logic which do not necessarily exist.
Robert Adams made a moral argument against the existence of these entities, as they make us powerless to do anything that would improve a situation.
possible worlds