It is demonstrated how to incorporate the traditional notion of a proposition as eternal and unvarying in truth value into a semantic theory like that of David Kaplan, by distinguishing among not three (as in Kaplan’s work), but four levels of semantic value: extension, content, content base, and meaning. Unlike the semantic content, the content base of a sentence may be temporally neutral, and may thus vary in truth-value with time. This semantic theory supports that generally unrecognized fact that the semantic content of a predicate, like ‘is reading’, is a temporally indexed attribute (re...

It is demonstrated how to incorporate the traditional notion of a proposition as eternal and unvarying in truth value into a semantic theory like that of David Kaplan, by distinguishing among not three (as in Kaplan’s work), but four levels of semantic value: extension, content, content base, and meaning. Unlike the semantic content, the content base of a sentence may be temporally neutral, and may thus vary in truth-value with time. This semantic theory supports that generally unrecognized fact that the semantic content of a predicate, like ‘is reading’, is a temporally indexed attribute (reading at t, t a time), and hence changes as the predicate is evaluated with respect to different times.