On a free market, shamans and doctors invest their own time and money and can lose their savings if their method does not work. In the long run only precise sci

On a free market, shamans and doctors invest their own time and money and can lose their savings if their method does not work. In the long run only precise scientific methods give reliable results while shamanism has random results. People vote with their money for the most efficient and better proved way to solve problems (provided kings, churches and governments do not interfere). Of course, this iterative process does not give you a short-term guarantee that you'll be healed, but neither does any sort of absolute authority. We don't necessarily need a lot of people to understand a lot of complicated things. We just need to not interfere when some people think they can solve things better than before, even if you think they are mistaken. Doing otherwise creates a larger scale hazard (cf. today's patent and regulatory environment).