Truth in Dreams

In one Cartesian argument for skepticism about the reality of the world, we are to assume that if we were dreaming, then were we to see hands in that dream, those would not be hands. Still, they would be dream-hands, in a dream-world, so dream-reference to them would hardly fail, or would it? If we think of someone dreaming about hands, then clearly those are not real hands; but, were this a dream (not a dream-within-a-dream, which is what our "dreaming" would then refer to), then what is meant by "real hands" within that dream would be dream-hands. You may well wonder if that would be the case, had we fallen asleep having already learnt the meaning of "real hands" in the real world. But presumably we learnt the meaning of "real hands" in this world, and if this was a dream then this world would be a dream-world. You could counter that if this was a dream, then we would still have learnt the meanings of our words in some higher realm, but as soon as we clarify what exactly we are talking about, by describing what we mean by "an external thing," we tie the meanings of our words to this world (the photo is from last year btw :-)