Empiricism, the idea that human knowledge derives from human sensory experiences, cannot be true. Whatever you are observing in the world, that thing could have been perceived in an infinite number of ways. Your actual perception of that thing, however, is unique and particular. Furthermore, everything about your perception that makes it unique and particular (i.e., everything that distinguishes your perspective from any other perspective that could be taken toward that thing) constitutes an assumption, a theory, about how that thing is to be perceived. All observation is therefore, as Karl Popper put it, theory laden. Thus we must acknowledge, contra empiricism, that ideas precede experience, and that, as David Deutsch has remarked in building on Popper’s insight, all we have is interpreted experience. This fact refutes the empiricist concept of “pure” or “direct” experiences, as well as the corollary doctrine that our ideas—which include our knowledge—can in any epistemologically relevant sense be derived from those experiences.