Another set of philosophical questions concerns the possible relationships between hallucinations and states of the brain. It seems unarguable that hallucinations arise from disorders of brain functioning but even this most natural assumption can raise philosophical puzzles. For example, if hallucinations and veridical perceptions (of ordinary, external reality) share common neural pathways in the brain, how can we distinguish them, either introspectively or conceptually? If the brain is a kind of generator of experiences (hallucinated or veridical), one might wonder how perceptual experiences (like voices or visions) arise from or are had by something as seemingly inert as a brain. And if experiences, including hallucinations, somehow arise from neural processes, this does not explain how they represent, refer to, or provide the kind of direct awareness of the items in our environment that they seem to. (There are, after all, no colors in the brain.) In response to these problems, some have suggested that, rather than conceiving of the brain as a kind of generator, it should be thought of as a kind of receiver (for sounds) or lens (for images). Then the brain would not be a source of perceptual experiences but an instrument for having them. In that case, a hallucination might not be a perceptual experience at all (a lens or a recorder does not experience anything), but a kind of trick played on the brain to convince it that it is in a state that it normally occupies when it does perceive (hear or see) something.