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 soul of religion and the matter 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 struggle to speak to each other.
Dualism then accepts physical realism, that physical things exist, and adds a mental reality to it, but how can different realities interact? If mind and body don’t interact, they are irrelevant to each other, but if they do interact, which comes first? If the brain first causes the mind, then it is like the whistle of a locomotive, a superfluous outcome. Conversely if an ideal mind first causes the world, isn’t it also illusory? Either way, if one is real, the other isn’t, or at best irrelevant. And if two realities are in conflict, why hasn’t heaven purged earth already, or earth corrupted heaven? That two independent causes both cause each other seems illogical.
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 world it describes now real, and theology calls the future it describes real, but given a choice between now and later, many prefer to focus on the now.