Hi hosepipe!!! I've been mulling over this question myself. It seems to me that if time is a mental construct, "a physical brain thing," it is so because there really is such a thing as time. IOW, the mind isn't creating time out of thin air, so to speak. Time is not an illusion of the mind; rather the mind somehow is awfully good at modeling the reality in which it participates. So this is not an either/or question, but a both question: Because time is objectively real, it can be "imaged" as a human "mental category."
Then agan, there is time, and there is timelessness -- the latter not being susceptible to direct sensory perception, but capable of being grasped in some fashion by the mind. Plato insisted that man lives at the intersection of time and timelessness. Christians say that the human person is mortal, and yet his soul has extension (or rather lives) in timelessness, or eternity. Humans actually participate in two different temporal orders, one we can directly perceive within the 4D "Minkowsky space," and one we cannot.
It's a difficult subject, isn't it?
Thanks so much for writing, dear 'pipe!
Exactly.. What I try to say when I propose the donkey and the spirit.. metaphor.. What we see in the mirror as ourselves our bodies is in one paradigm and what is looking back at us from the mirror the eyes of our spirits is rightfully from another paradigm..
Could explain what a human body dieing is all about.. A separating of the material from the spiritual.. Which is not really death at all.. but a metamorphosis.. And we have just proved what our spirit Is or Isn't.. The human body being a chrysalis.. for the production of many kinds of spirits.. with a thousand different butterflys being an example..
Others are able to perceive physical reality as four dimensional - three spatial dimensions and one temporal dimension (relativity.) This would be the Minkowski "space." I would venture that this is the limit of the unaided mortal perception, i.e. without mathematical reasoning and especially without the indwelling Spirit.
A few are able to mathematically envision additional spatial dimensions (string theory) either compactified (Kaluza-Klein) or expanded from the Big Bang. And a very precious few are able to mathematically envision additional temporal dimensions (Vafa, Wesson, et al.) Also, some physical cosmologists are able to mathematically envision timelessness and spacelessness from which geometry must bootstrap in order for there to be a physical reality at all and in particular, physical causation.
But in all of this - it is only Christians and a few blessed others such as Plato - who actually are aware of being alive in timelessness while yet in the flesh (space/time.)