It's not that life is a dream, but that the distinction in the way of putting the world together is waking life and in dream life is only a contingent one. The choice as to where to draw the line is a cultural one and a personal one and it can be freely changed. You might say that art is the presentation of common reality through the lens or apparatus of dreaming mind. It offers many small revelations, but whether these serve to unlock the latent potentialities of waking mind or to confine it more tightly within its compartments, by giving it a safe and defined place, is another matter. You might also substitute madness for dream here. The aim however is to undo the distinction, and only the distinction, tout court.