Everything we know about the world comes to us through our brain. Yet for each of us our own conscious mental world of thoughts and feelings is isolated and private. Despite several centuries of research on the brain, communication through language or gesture remains the only way we can discover the conscious thoughts and experiences of others. But if thoughts and feelings arise from patterns of neural activity in the brain, then it should be possible to directly decode such conscious experiences from brain activity alone. Recent advances in brain imaging technology raise just such a possibility, by showing that it is possible to accurately decode a person’s conscious experience based only on non-invasive measurements of their brain activity. Moreover, recent research demonstrates that there is substantial variability in how different people experience the same physical environment and that this can be indexed by structural and functional imaging of the human brain. Such ‘brain reading’ abilities may transform our understanding of the brain and provide important new medical insights, but also raise important ethical issues concerning the privacy of personal thought and behavioral predispositions.