If the brain in a vat gets perfectly simulated input, then indeed, there is no way to tell. Same thing if we live in a computer simulation. However, if such a

If the brain in a vat gets perfectly simulated input, then indeed, there is no way to tell. Same thing if we live in a computer simulation. However, if such a surrounding simulation 'errors' that can be noticed. Moreover, there is the rather pressing issue of 'being turned off'. Its a difficult (semantic?) discussion of whether you can notice your world being deleted, but the thought of unpredictable all-encompassing extinction isn't quite comforting. A better reason not to care, is the idea that there is nothing you can do about it. However, if we are being simulated, there is probably some observer who might react to our actions. Moreover, if we are in a computer simulation we might be able to trigger some 'bug'. So even that line of reasoning isn't clear cut. In the end, life does seem to be easier when you accept reality. Even more so because any way we have to influence the 'outside' is so infeasible as to be useless.