Part of the "Become Informed" Series, by WHP
Not only so little -- In many cases there isn't a molecule to be found (At 24x, 12c and higher). This controversy has been raging since the early 1800's when Hahnemann** began diluting out his medicines to avoid toxic effects. **Hahnemann is the Father of "modern" homeopathy
Hahnemann found that by diluting and succussing a substance (vigorous pounding or grinding) of a substance it not only becomes more dilute, but has an even stronger medicinal effect than the crude (or the diluted crude)
A great deal of the "homeopathy" becomes in the United States is or was done using potencies (strengths) where there are "molecules". In the old days, there were raging battles between the homeopathic doctors who used low potencies (say through 30x) and those using all manner of higher potencies, e.g., 200 and up. The high potency people were trying to bring the full range of homeopathy's potential into play and the low potency guys would respond by saying "but there's nothing there."
Right now the bulk of homeopathic medicines on mass market shelves is in Combination (two or more remedies combined), and the combinations are typically low potencies.
So for your friends who just can't stand the idea of no molecules -- Encourage them to use the low potencies (single remedies or in combinations). This isn't a political or religious question -- it's OK to use homeopathic remedies in low potencies. If they do use them they will see that there is action -- If they see action, great, they're over a hurdle. Now if they are fully "cured", fine, but if they aren't they can go to the next higher potency, and if that helps but doesn't finish, then they can go on up the potency scale -- Before they know it they will be beyond molecules and glad of it.
For those who simply must understand how it works here is the latest theory -- It is proposed by a physicist who explains that there are crystals in water and that even though there may be only a minute amount of water in the making of a remedy it is unique to that substance -- When the remedy is diluted and succussed the crystals maintain their identity, yet change enough to produce a different effect (higher strength).
That the mechanism of action remains theoretical is a function of money and time. If someone threw some money at the question it could be answered quickly -- If they don't we will simply have to wait -- Something homeopaths are good at doing.