The Christian Vanguard

Smart thinks that talk of “past”, “present”, and “future” can replaced by some reference to a subjects utterance. So “past” will be replaced with, “X is earlier than this utterance”, “present is replaced with, “X is simultaneous to this utterance” and “future” will be replaced with, “X is later than this utterance.” The same can be done for any sentence with a tense in it. When one utters “X is earlier than this utterance”, it could be objected that the word “is” in the sentence is tensed, and so even with the effort to phrase everything in a tenseless way, it is still necessary to smuggle in tensed language. Smart says we can amend the predicate to say, “X is earlier at this utterance” and referring to an utterance in this way makes no use of a tensed “is”. So for example, a tribe that had three sorts of numbers, that of being earlier than, equal to, or greater than the kings age, denoted by alpha, beta and gamma, but no tense is employed there either. 

In the A series of time, events have the position of past, present, and future. These positions are not permanent. Under the B series of time, events have the position of earlier or later than some position. These positions are permanent. A series can change positions because an event which is now future will eventually be past, but in the B series, if some event X is before some event Y, it will always be so.