Dream argument

The dream argument is the idea that because dreams can seem so real, we cannot be certain that we’re not dreaming right now. So, if we can’t be sure that we’re not dreaming, then maybe we can’t be sure that anything is real.

Imagine you're asleep and dreaming about eating ice cream. It looks and tastes just like real ice cream, but it's not actually real. When you wake up, you realize the ice cream you ate in your dream wasn’t real. The dream argument is like this, but with everything in your life: it could be just a dream that feels like it's real. So, you would never really know if anything was real or not.