It sounds like you're trying to re-frame the discussion from a context where homeopathy simply doesn't fit within currently understood models of the universe, into a context where it does and there simply is no evidence of efficacy. i.e., whether it "would be" good medicine or not is completely irrelevant, because we're talking about a treatment that doesn't fit at all within scientists' observation of the universe.

Or, to put it another way, tptacek once said (and I'm paraphrasing here) that if you were to choose a cryptographic algorithm, you would tend to want to bet on the one that can only be broken by a fundamental new discovery in mathematics. In the case of medicine, the opposite is true: we're currently discussing a medicine that would require fundamental new discoveries in several sciences in order to work.

> Conceivably it could have turned out to work in some way that violated previous medical understanding.

That's the thing: no, it couldn't have, not even conceivably. I'm really not generally pessimistic about the possibilities of new discoveries in sciences, but we're talking here about violating not just "previous medical understanding" but the violation of our current understanding of the foundations of chemistry, physics, and biology. This is not just "medical understanding", this is "our understanding of almost everything".

> Lots of things have done this – it’s one of the main ways understanding is refined.

This is mentioned often by laypeople when debates over our scientific understanding of the universe comes up, and it's wrong because it ignores the way in which our understanding has changed throughout history.

Science tends to refine its understanding of the universe towards a narrower and narrower minima. Since people like to point to relativity as an example of a radical change in understanding, let's take that as an example: let's start with Copernicus, who started with the hypothesis that the Earth revolved around the Sun, and then move on to Galileo, who further observed and refined the movement of the planets and other objects in the sky, and then find ourselves at Newton, who began to formulate the theories of gravity that described the laws of the universe behind Galileo's observations. When Einstein described relativity, his discovery didn't violate Newtonian mechanics or the entire body of 700 years of scientific observation and understanding. Rather, it refined it: the observed differences between relativity and classical Newtonian mechanics only show up at very large velocities or very large scales. Otherwise, everything actually works pretty much the way Newton described it.

Likewise with quantum mechanics: it's likely going to further refine relativity, but only on very, very small scales.

The proposed mechanisms for homeopathy don't require a refinement in our understanding of science, they require a complete contradiction of its very foundations.

> Besides which, as far as I know (which is not far) there is no fundamental principle of biology, chemistry, or physics that it breaks. It just so happens that water molecules and immune systems don’t work the way homeopathy would need them to.

I don't even know how you could put those two sentences next to eachother. :-) If "water molecules and immune systems don’t work the way homeopathy would need them to", then "there are fundamental principles of biology, chemistry, or physics that it breaks". You can't say, "it doesn't break anything, except that everything would have to be broken for it to work."

> While you could see this in terms of a violation of principles (in the same way that you can rewrite any false math theorem to 1 = 0 if you work hard enough)...

Actually, you can't. Every example I've seen of the "1 = 0" proof contains a very subtle mistake which violates mathematic principles. Sometimes, finding those mistakes is really really hard, but they're always there.

But, just to further drive the point home: if we were to argue that water could contain "memory", we would have to try to figure out how. First, are we talking about ordinary tap water, which contains trace amounts of various other chemicals? Or are we talking about "hypothetical" water, which contains only molecules of H2-0? If we assume the latter, for simplicity's sake, then we next have to determine where the energy for this "memory" is stored, how it's encoded, and what form it might take. Let's propose the simplest possible explanation -- which violates everything we know about cellular biology -- and say that this "memory" is basically some theoretical "frequency" that the "medicine" resonates with. All we have to do then is propose that atoms of hydrogen and/or oxygen can somehow store a frequency ...

If that happened in nuclei, I'm pretty sure it would break spectrometry, which would make it really hard for astronomers to observe the atmospheres of planets. If it happened in the electron shells, I'm pretty sure it would break the entire concept of ionization, since changes in frequency cause changes in energy levels of electrons, which cause them to interact with other atoms in various ways.

This is just one example; in fact, there is a huge body of scientific knowledge, built by hundreds of years of experimentation, postulation, and observation, that would all be directly contradicted by any proposed mechanism for homeopathy.

> But I’m not a doctor, biologist, chemist, or physicist, so I guess it could be.

This is bugging me more and more, lately. If someone isn't a doctor, biologist, chemist, or physicist, then I don't see how that person could say, "...but I think they might be wrong!"