1. is a context related to c in which the time is specialized to have the value t . We may have the relation Here is the assertion that the proposition p holds at time t . We call this a lifting relation. It may be convenient to write rather than , because this lets us drop t in certain contexts. Many expressions are also better represented using modifiers expressed by functions rather than by using predicates and functions with many arguments.
Actions give immediate examples, e.g. rather than .
Instead of using the function , it may be convenient to use a predicate and an axiom This would permit different contexts c 1 all of which specialize c 2 to a particular time. There are also relations concerned with specializing places and with specializing speakers and hearers. Such relations permit lifting sentences containing pronouns to contexts not presuming specific places and persons. There is a general relation specializes between contexts. We say when c 2 involves no more assumptions than c 1.