Soledad Aznarez You believe the philosopher René Descartes led us astray. In what way? He’s the one who argued that the mind couldn’t be just the brain, couldn’t be just the body, that it had to be a different kind of substance altogether. It’s one of the greatest mistakes in the history of thinking. And we have been trying to undo that mistake ever since. Certainly, I have. Why has it been so hard to overturn this picture of the mind?