Even if our entire Universe is just a dream, it does not change anything. It still exists, even in the mind of a five-dimensional mushroom. Amanita can explore this part of his mind, imagining himself as a man and using scientific methods. Everything that anthropocentric science requires from this "mushroom" is that his dream was consistent, logical, and obeying mathematical laws. This requirement is, indeed, a falsifiable hypothesis, in a contrast to the hypothesis suggesting the existence of a dreaming mushroom.