Any truth that can exist in one can exist in the other. For this reason there is no precise way to understand whether an experience was dreamed or not. Arguments to the contrary are purely speculative, based on personal experiences and perhaps the experiences of others, but that is not enough. Just because one person might not feel pain during a dream, which means some sort of differentiation between the two states, doesn't mean another person doesn't feel it. Since all the evidence against this argument is purely speculative and circumstantial, it shows that we cannot demonstrate consciousness at any given time with Cartesian certainty. A waking state exists, however, our ability to differentiate it from a sleeping state is impossible, which leads to confusion about experiences. Having Cartesian certainty about whether or not we are dreaming at any given moment allows us to evaluate all the other aspects that could distort our results. Since we could fall asleep at any moment, who is to say that our knowledge and experiences are not all dreamed? The brain, although a complex mechanism, is not complex in producing the ideas we have experienced within it. We can form new ideas based on our experiences, but the basis of them must have been experienced at one point or another. Our brain needs references for knowledge, and to know absolute truths, we need to understand that some truths may not be so