The ideological war between western science and religion grew, until Descartes proposed the truce of dualism, arguing that “I think, therefore I am”. Why not have mind and body, the spirit of religion and the objects of science? This divided scientists into atheists who believed only in the physical world, theists who believed in a world beyond it as well, and agnostics who couldn’t decide. This marriage of convenience worked for a while, but today science and religion barely speak to each other.
The problem with dualism is how can different realities interact? If mind and body don’t interact, each is irrelevant to the other, as the mind can’t affect the body. Or if they do interact, which was first? A mind that emerges from a physical brain is like the whistle of a locomotive, superfluous to the main action. Conversely if an ideal mind made our world, why did it make evil? Either way, if one is real, the other isn’t, or at best irrelevant. And if the two realities are in conflict, why hasn’t heaven purged earth already, or earth corrupted heaven? Or if mind and body are sides of the same coin, what is the coin?
Facing such challenges, dualism is less popular now than it was. One reality is simpler than two, so why not just have physical reality? Science calls the physical world it describes real, and theology calls the spiritual future it describes real, so given a choice between a theory of now and one of later, many prefer the former.