What?
If everything in the world is false. What remains? There is thought.
Can that thought be an illusion? Sure. But where is it coming from? Something must be real.
You're talking about
Brain in a Vat which while the person is an illusion. There's still a brain behind it all. There must always be something creating thought. It's like the matrix/vanilla sky and everything else.
The only way you'd be able to argue that is if you claim that we're just programmed AI. But what then defines real? are programmed AIs any less real? When you think about it. The human body from an athiestic point of view, is just a biological robot that is programmed. Current understanding of consciousness is that it's just random neurons firing.
End of the day, the only thing that we can be certain is that thought exists. Whether we'd be biologically or artificially programmed.