All very straightforward, you might think, even if somewhat misconceived. However, "straightforward" it certainly is not. One of the reasons humoral theory continues to hold such sway is because it is so involved and complex. Its numerical harmony (the four elements, the four humours, etc.) allows for endless refinement and invented complexity.I would add to that the power of certification. Whether it's young men attending academies to learn principles that set them apart from the public, or the divine who cultivates a privileged understanding of spiritual verities, there's a benefit to being accorded a position where your opinions cannot be challenged.
I see the same mixture of nonsense complexity and appeal to authority in the economists of today. They are the high priests propagating the special, liquidity-based healing that they say our economy needs.