A great many of the philosophical debates about time concern what is real. They concern (a) what is real in order for there to BE time; (b) what is real IN time. These both play a role in questions about illusion.
When it comes to whether or not some experience is an illusion or not, what is real can matter. It can determine the real structure of experience, and what is real which we can experience. Given perceptual experience seems, at least, to be of real things, this can affect whether or not a particular perceptual experience is illusory. For example, if it seems that you see a large circle surrounded by smaller circles, it matters if there really is a large circle out there so surrounded by smaller circles. If there is, there’s no reason to think there’s an illusion. If there is not, there is an illusion (or, perhaps, more accurately, an hallucination, but ignore that distinction for now).
So, for example, if only physical things are real, this will determine whether or not certain kinds of experiences are illusory — those of non-physical things — if there are any.
Not all questions about what is real need matter to this. For example, the question of whether or not merely possible worlds are real may not matter to whether or not an experience is illusory.
However, I think time matters. Different views of time hold different views about what is real in time. And I argue in my work, e.g., in my papers, that perceptual experiences happen in time. What is real about perceptual experiences is an example of what is real in time.
The reason why there is this difference between time and something like possibility is that, whatever we say about possibility, we hold that the real structure and relationship to things in perceptual experience is restricted to the actual world. Further, there is only one actual world; there are not a multiple of actual worlds. As such, that existence contains more than one possible world makes no difference to the real structure of experience. The real structure of experience does not change with the number of real possible worlds because it stays within one and only one world.
However, the parallel case for time is both/either not so clear and/or disputable given different views of time. The parallel view for time is that the real structure of experience is only at one time (the present time). Further, there is only one present time; there are not a multiple of present times. As such, that existence contains more than the present time makes no difference to the real structure of experience. The real structure of experience does not change with the number of real times because it stays within one and only one time.
This view of experience as it exists in time can be disputed. I argue that there are even good reasons to dispute it.
As such, the possible and the temporal are not similarly innocent with respect to the structure of experience.
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