The whole concept of "this is just a big dream" can't hold true if you have common sense. It's like the Christian Scientists cult saying that disease and death are just conditions of the mind, and if you defeat the thought, then you defeat the malady. That's just silly. In order for anyone to have any kind of discourse on existence, you have to come to the table with the basic assumption that you can trust your senses. True, your senses can be deceived, but that's why you have five of them. The sensations you perceive form a consensus of the senses, which you interpret and react to.