 Noninvasive ways of inferring neural activity have led many to worry that mindreading is possible, not just in theory, but even now. Using decoding techniques fMRI can be used, for example, to reconstruct a visual stimulus from activity of the visual cortex while a subject is looking at a scene or to determine whether a subject is looking at a familiar face, or hearing a particular sound. If mental content supervenes on the physical structure and function of our brains, as most philosophers and neuroscientists think it does, then in principle it should be possible to read minds by reading brains. Because of the potential to identify mental content, decoding raises issues about mental privacy.