Just focusing on what exists now seems a bit exclusive. And if we include everything that has ever existed as part of the universe, why not include t… - John Barrow

The Greek tradition was a complete contrast to that of the Far East. ...the Greeks placed logic at the pinnacle of human thinking. Their sceptical attitude towards the wielding of 'non-being' as some sort of 'something' that could be subject to logical development was exemplified by Parmenides' influential arguments against the concept of empty space. ...He maintained that you can only speak about what is: what is not cannot be thought of, and what cannot be thought of cannot be. ...more unexpected was the further conclusion that time, motion nor change could exist either.

Scanning the past millennia of human achievement reveals just how much has been achieved during the last three hundred years since Newton set in motion the effective mathematization of Nature. We found that the world is curiously adapted to a simple mathematical description. It is enigma enough that the world is described by mathematics; but by simple mathematics, of the sort that a few years energetic study now produces familiarity with, this is an enigma within an enigma.

...logical contradictions will inevitably arise and the laws of the simulations will appear to break down now and again. The inhabitants of the simulation—especially the simulated scientists—will occasionally be puzzled by the experimental results they obtain. The simulated astronomers, might, for instance, make observations that show that their so-called constants of Nature are very slowly changing.