All the empirical objects that I perceive around me are structures of sensations: sensations of color, tactile sensations such as hot and cold, hard and soft, and rough and smooth. But sensations are supposedly manufactured in the brain, out of neural signals delivered from the sense organs. This leads to two questions: how do they get out there, into the real world; and if sensations are unreal --- they exist only as long as they are perceived --- and the real world is composed of sensations, is the real world really real?