We rely on their expertise because medicine is a huge, complex and ever-changing subject that most of us simply don't have the time to learn in enough detail, or to keep up to date with. We depend on their professional integrity, on their diagnostic skills, on their knowledge of the latest medicines and treatment regimes for illness and from where this can be obtained.
We expect their judgements to be rational, informed, evidence-based, impartial and, if required, demonstrably justified. In short, we expect them to be scientific.
But what if they behaved like priests?
What if they told you you must be suffering from an illness because it said so in a 3500 year-old book, and that you needed to say special words and incantations to be saved from it?
What if they told you that, even though there was no evidence for cancer, they were going to prescribe a course of chemo- and radio-therapy anyway because absence of evidence is not evidence of absence, so it is best to assume cancer, just in case?
What if you went to them with a headache and they told you it must be imaginary because they had faith that there was nothing wrong with you and that your problem was that your faith wasn't strong enough and your headache was just a test?
What if you went to them for contraceptive advice and they told you you were evil and should say magic spells to prevent something nasty happening to you later? And no, you just have to have more babies or stop having sex.
What if your were diabetic and they said they would cast some magic words over your because that would be better than medication?
What if they told you that incantations, special hand movements and sprinklings of magic water would cure your child of a virus infection?
What if they told you bunions were caused by an evil spirit which you had allowed to enter your body, so it was your own fault?
What if they told you that modern medicines were not mentioned in their favourite old book of Bronze Age origin myths so they were no good and should not be taken?
What if they told you that they got all their information from an old book which had not been updated for nearly 2000 years; that they never read any modern books on medicine because they were all lies and they knew this because they disagreed with their favourite old book?
And what if you were clearly disturbed and felt compelled to go to them every week and give them a lot of money, and they told you this was a good thing and that you should give them as much as you could afford, at least 10% of your income?
Would you think you have a really good doctor, or would you look for a proper one and report this one for malpractice?
Strange then that exactly this behaviour is tolerated in priests, pastors, vicars, imams, rabbis and other people who make a living as religious clerics.