|Add sleeping, dreaming, and waking|
to the list of our existential uncertainty.
What is an obvious and immediate consideration when we recognize our own existence? Any question of our experience immediately brings up its existence separate from us. What is it? Which is 'more' real, the logical source of our experience that lies outside of experience (object) or that which recognizes and becomes aware of that occurrence.
The branch of philosophy retroactively entitled "continental philosophy" could be seen as deriving itself from this single issue. In asking that one question we are forced to consider not only our experience, old our existence and finite, and the apparent cleavage between representation and source, numinon and phenomenon. We must also crack open a dank can of "What the Fuck" (it comes in regular and diet) in contemplating the limits of the methods we might use to explore these issues. And so epistemology joins cosmology. Is the real real? Emphasis floats in one philosophy, and one generation, and the next.
Frankly, the words start to sound just like noise being made by flapping lips.
Be that as it may, here are some different perspectives:
Perhaps as this random guy I found on YouTube says, "Time and Space do not exist at all."
Compare this with the interpretation of this issue
as Buddhism entered the West through Schopenhauer,
(first here in discussion of Kant and representation.)
He told us so: