What was will never not have been.
(One might think that a simpler variant would do: "What was will always be." However, it could be argued (I do not know how successfully) that the simpler variant has the substantive entailment that now is not the last moment of time, and perhaps even the entailment that time has no end, thereby making the thought far from tautologous. These kinds of departures from tautology are easy to fail to notice but can be important in some philosophical contexts. Deep Thinking requires care.)