Computation is as real as math.

The halting problem, which asks whether a program will eventually stop running, is forever beyond the reach of any computer.

Or any human.

People have fumbled that recently: the halting problem isn't just incomputable, it's a paradox. It turns 'anything is computable' into a contradiction. It has no solution. When someone brings it up to dismiss the possibility of AGI, tell them to fuck off.