ratiocinator
Lightly seared on the reality grill.
Are you familiar with the concept of solipsism? (genuine question btw, not trying to be a smart arse).
Yes - but it's a bit of a dead end. In practical terms, there is a qualitative difference between (what appears to be) the outside world and what goes on in our minds and the former is inescapable and (appears to be) shared between everyone, so if it isn't real, it might as well be.