Descartes was neither the first nor the last philosopher who wrote about the pineal gland, but he attached more importance to it than any other philosopher did. Descartes tried to explain most of our mental life in terms of processes involving the pineal gland, but the details remained unclear, even in his own eyes, and his enterprise was soon abandoned for both philosophical and scientific reasons. Even so, the pineal gland remains intriguing in its own right and is still intensely studied today, with even a whole journal dedicated to it, the Journal of Pineal Research.