The great philosopher Descarte divided the world into 2 substances Mind and Matter. Apart from the debate about what is Substance and why Mind should be divided from Matter, a hugely pragmatic historical event occurred. In the 17th century, Decarte allowed people in the western tradition to pursue science without metaphysics. Inadvertently, Descarte codified a division between religion and natural Science, between Church and science. The Thinker could pursue either science or religion separately.
This ability to pursue only Materialism and Mechanics without worrying about Metaphysics and the Church led to progress in Europe which made Europe more powerful and wealthy than any other region of the world.
So this philosophy of dualism was true in that it was successful.
Of course there is a difference between Truth and success. Does this dualism, this pragmatic division between metaphysics and materialism make a division where there should not be one? Also, has this division become unfair and given all to materialism?
In the light of modern science many metaphysical concepts are just ignored as obsurd. However, in truth we need to tread lightly here because material science has yet to explain consiousness. Material science has yet to explain mind (Cognito) or to develope a consious machine (strong AI.)
Yes, there is a lot of technicality involved in the field of the Philosophy of Mind but no one really understands or has proved Conciousness. Conciousness is so different from the rest of nature we can see why Descarte considered it a different Substance.