 The argument is clearly valid. To defend presentism, we must deny one of the premises. But each premise appears independently plausible. (1) takes truth to be a monadic property, e.g., being true, and reflects a commitment to serious actualism: if P instantiates being true, then P exists. (2) takes propositions as truth-bearers (or “truth-value bearers”) and follows from the simple claim that there are truths about the past (more on this in  §6).  (4) takes propositions as complex entities and reflects a commitment to the principle that a complex depends for its existence upon things that constitute it. The remaining premises, (5) and (7), follow straightforwardly from the two metaphysical theses at issue, the neo-Russellian view of propositions and presentism, respectively.