How clinical trials are done, how the evidence is gathered, how that is turned into action and decision-making.
But, he argues, if evidence-based medicine is done behind closed doors, it paves the way for quacks to walk in and exploit the public's fears.
He makes a good point in that I generally trust a person in a white coat telling me something is good for me. I also believe in the efficacy and necessity of inoculations against disease. But I don't know how it works, and the argument of requiring a medical degree sounds a bit pompous. It can be explained.
Conspiracy theorists and quacks have been around for a long time and their behaviour isn't about to change. There are also a lot of people who will have their beliefs and ignore the evidence. They have a different relationship to the truth, as Dr Goldacre says.
If you want your children to live, get them vaccinated. If you want the best chance of being cured, go to a doctor. If you want to try something that makes you feel a bit more comfortable about life, the universe, and everything, then sure, homeopathy's an option. They'll probably tell you how it works in great detail. But according to Dr Goldacre, it's a pity medical science doesn't do the same.