It's the damn genes revolting against the host. Physical pain is the result of genes revolting against the body, mental pain is the result of memes revolting against the brain. Disease thus, happens because some group of genes de-program the corresponding carnal sector they are responsible for maintaining, or, the sector they were responsible for having had created. Science, as few of you may already know, has followed the road of the Dodo. It's them who actually abuse the general consensus of what constitutes science, and believe me, a true scientist, or a multi-scientist, like me, a rare species indeed, according to my definition of science, would simply HAVE to be insane.
Many people stick to one viewpoint so badly that they go insane anyway.
But this is perhaps preferable to investigating many different paradigms. But I digress. As you go down to cells, the entire mechanism of the cell, is one huge intelligent factory. The constituents of the cell, are MORE intelligent than the cell itself. Thus, mitochondria, golgi bodies, the nucleus, etc, actually are hegemonial sub entities, held in place by the power of the cell's organization.