Truth, Lies & Uncertainty - Scientific American: In this special issue of Scientific American, we set out to explore how it is that we can all live in the same universe yet see reality so differently. Basic science illuminates the deep roots of this phenomenon. Even in physics and mathematics, truth is not entirely clear-cut. And mounting evidence from neuroscience indicates that our perceptions are not direct representations of the external world. Rather our brains—each one unique—make guesses about reality based on the sensory signals they receive.