Additional
Information: Modailty deals with what is necessary and what is possible; e.g., a necessary truth is a proposition that could not have been false, a necessary existent is an entity that could not have failed to exist, etc.
Modality Sites:
Actualism
The thesis that there are no merely possible entities; from the Stanford Encyclopedia by Christopher Menzel. http://plato.stanford.edu/entries/actualism/
Modal Fictionalism
Survey of the view that claims of necessity and possibility are to be construed as fictional claims; from the Stanford Encyclopedia by Daniel Nolan. http://plato.stanford.edu/entries/fictionalism-modal/