Double-Index Temporal Semantics and Retrogradation of Truth

According to the principle of retrogradation of truth (RGT), if p is true today, then it was true in the past that p would be true today. While this principle is trivially true in deterministic temporal semantics, it is surprisingly not validated in many indeterministic temporal semantics. Yet, it is a very intuitive principle, and such intuitiveness has also been recognized by many open futurists. However, its validity is usually acknowledged only at a post-semantic level. In this paper, we present a semantic system that validates the principle of retrogradation of truth. This system has two indices: one representing the evaluation moment and another representing the moment at which the world has arrived.