 Broad’s claim (a) was vindicated by the fact that McTaggart’s argument has received serious attention from most subsequent philosophers who pondered the metaphysics of time. Much of this debate concerns the relative relations of the two series. Is the A-series fundamental and the B-series derived from it, or vice versa; or does, perhaps, one series supervene upon the other? In the formal mode, the questions become whether the B-series may somehow be reduced to, may be defined in terms of, the A-series (or vice versa). These debates concern mainly language rather than physics and will not be considered  here.[2]