Ontology is the study of being. Ontologists ask questions like "What does it mean to say something exists?" The ontology of time is therefore the study of what it means to say that time exists or that something exists in time. In other words, what is time? I discuss the ontology of time in some detail in Sense and Goodness without God (pp. 88-96).
In response to what I wrote there, Dave Matson asked:
Why should time be defined in terms of relativity physics where, presumably, it means a fixed future? I would think that time, as defined in quantum mechanics, would be equally preferable. As defined in this latter sense, time is presumably compatible with an undetermined future.
If we accept time as defined in relativity, then it seems that physicists would have to accept that there are "wheels within wheels" within quantum mechanics, which most physicists deny. That denial suggests that time as seen in quantum mechanics is defined differently than in relativity physics. One view seems compatible with a fixed future whereas the other does not obviously fit into that mold, if at all.
So arguing for a fixed future on the basis of relativity theory is tantamount to assuming that its definition of time should be preferred. Therein, I see a problem.
In answering this question I will use RT for Relativity Theory and QM for Quantum Mechanics. And I will not repeat what I said in my book. So if you haven't read it, though you don't have to in order to understand what follows, you probably should read it before commenting on any of this.
Personally, I don't care all that much if nonbelievers prefer to call themselves agnostics rather than atheists. I think by now most everyone knows these are the same thing (after all, either way, you don't believe in God). And eventually the social stigma attached to the latter will float over and latch onto the former anyway, leaving no place left to hide. Well, okay, maybe the squeamish atheists will once again invent some new word to call themselves, so they can confuse a prejudiced society into not realizing they are (gasp!) really atheists. But that will just go the same way. In the end, the advantage will be lost, yet another word will have to be invented to hide behind, and 'round and 'round it goes. Good luck with that.
For me, this is all just a social game, semantic trickery, that is hard to have sympathy for, but I can't honestly criticize nonbelievers who want to avoid the social stigma falsely attached to a maligned word. Prejudice in this country, in some places and situations, is certainly real and harmful enough to justify a desire to dodge it. If black people could pretend to be white, I'm sure some of them would. This is frequently enough true for gays that they have a whole terminology of social disguise (like "in the closet" and "beard"). You can't condemn this until you've walked a mile in their shoes.
There is also a silly and heated debate (even so far as to cultivate outright rage) between atheists and agnostics as to who is really what. Of course, these terms don't even have a single meaning. Just as "atheist" can mean "denier" or "unbeliever" (generating the rather lame, confusing, and misleading terminological distinctions of "hard" and "soft" atheist or "positive" and "negative" atheist), so can agnostic mean "undecided" or "dunno!" The latter is more etymologically and historically correct, since agnosticism is supposed to be the formal position that one cannot know whether God exists or not (whether by definition or as a contingent fact of a particular agnostic's limited access to relevant evidence), but the former meaning is still very common in actual use, and both have crept into other contexts (so, for example, you can be an "agnostic" now, in either sense of the term, as to whether Robin Hood actually existed).
