According to Cicero, "there is nothing so absurd but some philosopher has said it." I'm not sure just what it was that prompted this comment. I like to think that there are limits to absurdity, or at least limits to the deliberate promulgation of absurdities as fact, but I confess I'm given to wonder now and then.
Consider, though: there are, or apparently were, philosophers who are or were unconvinced of the existence of an "external world" independent from our minds (dealt with in prior posts) or perhaps more properly that its existence cannot not be demonstrated to their (and therefore appropriate) satisfaction, and that mind and body are in some sense separate, and that Forms of absolute, perfect reality exist regarding which that which we experience is but a poor facsimile, and that we can't know just what "things in themselves" (like, for example, the computer on which I'm typing at this moment) really are; so, perhaps Cicero was right.
I'm doing some reading at the moment regarding the question whether the past is real. Some philosophers feel it isn't. Some, unsurprisingly, think it is. Most of us common folk, I think, would maintain that it was, but is not now. Most of us would probably assert that in the past, Roman legions marched around Europe, dinosaurs walked the earth, galleys manned by slaves were used for ocean transport. However, that is no longer the case. So, Roman legions, dinosaurs and such galleys certainly were real, but as they no longer exist, they can't be said to be real now.
A philosopher may be inclined to say, however, that we have no business referring to the past as real in any sense if it no longer exists, or that we can't state anything regarding what happened in the past, past events, past people, without purporting to come to conclusions regarding that which does not exist, which we cannot do legitimately. How can we rely on our memories, or even records of the past? There is no way to verify them, properly.
Some might question this kind of view, though. There is now evidence that certain animals existed which no longer exist. There are buildings we see which must somehow have come into existence, unless we're satisfied in thinking that they suddenly appear at the time we first encounter them. There are people we knew who are no longer present. Isn't it reasonable to infer from such evidence that there was or were some animals, things, people but now there are not?
Time is I think a particularly difficult subject for philosophers to analyze and explicate now, because physics has significantly preempted the field, or at least complicated it. In the realm of physics, there be dragons I certainly cannot slay, in any event. Physics may eventually ascertain that the past continues to exist in some sense, or can be retrieved, or perhaps indicate that there is a possibility of time travel to the past (if it has not already done so). However, until that occurs, just what can be said about the past? What is it?
In answering that question, I'd be inclined to apply some variant of Peirce's pragmatic maxim (he formulated several versions of it). This would entail defining it by reference to its practical consequences. The past is something that we recall, sometimes with pleasure, sometimes sadly. It thereby and in other ways can effect us and our dispositions and our lives. It can be used as a reference. We can make decisions regarding what is transpiring now based on what has taken place in the past. The world we interact it was in many respects shaped by the past; is a result of the past, and knowing the past can help us understand the world, ourselves and our fellow participants in the world.
The past is clearly something we think about, and something that influences us and how we live and act now. In that sense, it is clearly real now, i.e. it is a part of our world, our reality. Isn't that sufficient for our purposes? Why could or should it be "real" in some other sense? In what way does it matter whether if is "real" in some other sense (again, given the extent of our abilities and knowledge in the realm of physics at this time)?
No doubt I'm just demonstrating yet again why it is I'm not a philosopher; but once more I wonder why it is we devote ourselves to questions the answers to which, and problems the resolution of which, seemingly will make no difference to how we live, and what we do.