As promised, it's time to debunk homeopathy. Homeopathy is a type of "medicine" that originated early 19th century. Perhaps at the time, homeopathy might have made sense, and may even have been safer than other practices of the time. But with today's knowledge, homeopathy is clearly based on false premises. Homeopathy cannot possibly work, nor does it. The fact that homeopathy is accepted as alternative medicine, I think, casts serious doubt on all alternative medicine. If so-called "alternative" medicine cannot distinguish between practices that just might work if we thoroughly tested them (ie herbal medicines) and practices like homeopathy, which cannot possibly work, then it is worthless.
So what is homeopathy? Homeopathy is based on the idea that like cures like. In other words, if you have a cough, you take something that causes coughs. The idea is that everything has a potential to cause symptoms and to cure them. Obviously, we would only want the curing potential. Homeopathy solves this by a process of dilution. The more the remedy is diluted, the greater its curing effect, and the lesser its negative symptoms.
Every step of the way, this simply does not make sense. Why in the world should like cure like? Sure, that's how vaccines seem to work, but that's because vaccines work with the immune system. Homeopathy has no such rationale. In fact, homeopathy does not even deal with the sources of disease, like bacteria, or viruses, and so forth. Homeopathy only looks at the symptoms. So like cures like, even when the two likes have completely different causes.
And the dilution! By homeopathic logic, things become stronger when you dilute them. So if you drop a tiny bit of medicine into the ocean, you might kill all the fish with an overdose. That means that if you accidentally contaminated the ocean with a single drop, you should put in a couple more tons of the stuff in to keep it from getting too dilute. Oh, but I guess they say dilution only increases the strength of the good effects, and not the bad ones. Isn't it lucky that these little molecules are able to distinguish good and evil?
As a matter of fact, typical homeopathic medicine has been diluted so much to the extent that there is no longer any of the original medicine. Early homeopaths obviously did not know about Avogadro's number. At normal sizes, any dose of medicine consists of on the order of 10^23 molecules in it. If you dilute this, you will reduce the number of molecules in the dose. Let's say that the number of molecules is reduced by a factor of 10 for each dilution. After 23 of these dilutions, you'll have on average one molecule in the solution. As if that weren't enough, the medicine is diluted even more. You can't have a fraction of a molecule left over, so the end result is that it's extremely likely that there is not a single molecule left. All you have is water.
But let's not attack a straw man here. I'm leaving out one supposedly important detail. At each step of the dilution, the solution undergoes a process called succussion. This involves shaking the solution vigorously, which I guess releases the spirits from it or something. Modern homeopaths would say that this impresses upon the water a "memory" of the chemical. I would have thought that any structures in the liquid would be destroyed by the slightest shaking. Even if you could create stable structures in liquid water, whatever reason is there to think the water's "memory" would have the same effects as the original medication? Homeopathy is basically postulating magic water.
But if so many educated people believe homeopathy is effective, surely there must be at least a little truth to the claims, right? Well, no. The first thing that you learn from skepticism is that there are countless cases in which the masses have fooled themselves. People tend to rely on anecdotal evidence rather than experimental evidence. They say, "It may not make sense to the scientists, but I've still seen it work for a lot of people." But anecdotal evidence is extremely vulnerable to confirmation bias and small sampling errors.
Another problem is that people underestimate the placebo effect. A placebo is basically a sugar pill that misleads people into thinking that they have taken real medicine. When comparing people who have taken a placebo and people who have taken nothing, the placebo group tends to do better. This is called the placebo effect. Homeopathy is essentially a placebo, except it's made of magic water instead of a sugar pill. To filter out the placebo effect, experiments must compare the effects of a medicine with the effects of a placebo. This is impossible to do with anecdotes. All the apparent good effects of homeopathy, if any, are basically a result of the placebo effect.
I hear that homeopaths tend to be really nice people who give their patients ample attention, which in itself may be good for the patients' health. Now if only those homeopaths would add real medicine to their practice, rather than magic.
For further reading (also, information on studies disproving homeopathy), I recommend the Skeptic's Dictionary.