You are confusing (and conflating) the notions of "axiom" and "knowledge." Knowledge often comes from learning, and learning often comes from considering new evidence as it is discovered. (We didn't know about miniscule critters that could kill us until the invention of the microscope, for example.)
No, I am not confusing or conflating the two. An axiom is a self-evident or highly accepted fact from which other things derive. Knowledge is the acquired facts and synthesis of data. Axioms can therefore direct how we use knowledge, like to what goals do we apply the knowledge we have.
It's worth noting, however, that acquiring additional knowledge can potentially change which axioms a person bases their work on. Axioms help direct how knowledge is applied (for example, using medical knowledge of health to either help or harm), and knowledge can alter what a person uses as their starting axiom (as in, changing a religion due to acquiring more historical facts and then re-analyzing everything they thought about ethics).
So, yes, medicine is totally relative to what is presently known. Physicians facing unknown threats and symptoms are often required to make their best guess. And if that's all they've got, I'm not prepared to call them "bad" doctors for making the effort.
Same for ethics.
Can you explain why you think the field of ethics is more relative/subjective than the field of medicine?
Both start with an axiom, and then (poorly or skillfully, to varying degrees), use knowledge to try achieve the goals of those axioms.
Example Doctor
Axiom: It is good to optimize the health and well-being of consenting humans, based on certain metrics such freedom from disease, healthy body composition, motion, longevity, etc.
Knowledge sources: Medical school, published research studies, years or decades of clinical experience.
Example Ethicist
Axiom: It is good to promote the happiness and well-being of as many sentient beings as possible and to reduce the suffering of sentient beings wherever possible.
Knowledge sources: PhD in philosophy from studying the major ethics systems of the world, published studies on what promotes happiness or life satisfaction and what does not, published studies on how animals may perceive pain or happiness, economics, metaphysics, etc.
Which is just what I said. But what if one of your "axioms" is "God says you are to cut the foreskins off baby boys!" Is this based on "solid evidence?" What evidence? Is it rational? In what way? Let me point out, for example, that there are religious Christians who would deny a medically necessary (and beneficial) blood transfusion to their own child for just such an "axiom."
No, I don't consider it to be rational or based on solid evidence, because the axiom in this case (that the Bible is the word of God) is likely untrue. If people base their ethics on appeasing a god, but it turns out that this god never existed or that it does exist but they're using the wrong scripture, then that won't go over well.
A similar example in my view would be a doctor whose starting axiom is less than ideal. For example, say a doctor starts with this axiom: "My job is to extend patient lives as long as possible". At first glance that might be okay, but in practice, that could resort in sacrificing a patient's well-being to increase longevity, or to spend millions of healthcare dollars within the last six months of a patient's life trying desperately to prolong it without good reason, while increasing patient suffering when the patient is gravely ill and no longer wishing to live. It might be well-meaning, but in this case, was built on an axiom that is fragile and open to significant counter-argument.[/quote][/QUOTE]