The 17th-century Dutch philosopher Baruch Spinoza wrote that the "mind is the idea of the body." Near the beginning of the previous decade, the Portuguese-born neurobiologist Antonio Damasio provided scientific support for Spinoza's philosophical claim. This month, scientists from Ecole Polytechnique Fédérale de Lausanne in Switzerland published a paper in Current Biology that states the mind is not only the idea of a real body but also can be the idea of bodies that do not exist—ghosts. Two approaches led them to this conclusion: one, an analysis of people with lesions in specific areas of the brain; and two, a trick played by a robot on people with normal brains. What appeared in both cases is called "feeling of presence"—a ghost. We haunt ourselves, our houses, our walks in the park. But the discovery the scientists made in these late times of hard data and matter was already known long ago (the 19th century) by the soul of the American poet Emily Dickinson:

One need not be a chamber to be haunted,
One need not be a house;
The brain has corridors surpassing
Material place.