Scepticism and religion

[robvalue]

Just the "dream" problem is enough in itself to stop absolute certainty.

How can you be sure you're not dreaming?

You can't. You may be in a dream where things make perfect sense to you and you're absolutely certain of something within the dream, but once you wake up, it makes absolutely no sense at all. So the certainty is subject to the nature of whatever "reality" you are experiencing, whether or not it is actually "real", whatever that even means!

You may come up with criteria which proves something is not a dream, and everything around you meets those criteria. But you may still be dreaming, and simply think these are valid criteria.

This is an impossible problem and apart from being interesting in itself, it's not useful to raise as an objection to anything. All we can do is assume we're lucid and real, and plow on to the bet of our abilities.