Are the principles of Homeopathy scientifically valid

Are the principles of Homeopathy scientifically valid?

Vital Force

Hahnemann's concept of a vital force and its disturbance as a cause of disease, while plausible in 1815, is not accepted widely today. No one has ever measured or observed such a vital force. Modern medicine has had great success in identifying the cause of diseases. The discipline of Pathology, which did not formally exist in Hahnemann's day, is devoted to the study of the causes and characteristics of disease. The ideas of Hahnemann predated important discoveries such as those of Pasteur (1859) Lister and Koch, which showed that microbes were the cause of many diseases. Many of the diseases that plagued patients in Hahnemann's day (tuberculosis, syphilis typhoid fever, cholera) are now curable by the use of modern medicines. In fact it was the scientific advances of the late 19th and early 20th centuries that led to the rapid decline of Homeopathy.

Like cures like

There is no scientific evidence supporting this principle. This principle is based on attempting to match a pattern of symptoms, rather than an understanding of the underlying mechanisms involved.

Some proponents point to the use of vaccination as being similar to the use of nosodes (infected tissue or isolated infectious agent) in homeopathy. However, they are quite dissimilar in practice. Vaccinations used live or altered infectious agents in small (but active) concentrations to stimulate the immune system to prevent an infection. There are many documented vaccines that prevent disease in this way (e.g., rabies, yellow fever, polio, measles, etc). Nosode use in homeopathy consists of a small piece of infected tissue that is pulverized and diluted in alcohol, followed by serial dilution to infinitesimal levels.

Dynamization

The process of dilution combined with succussion to increase healing potency runs counter to the modern principles of Pharmacology. The pharmacological concept of the dose-response relationship states that as dose increases, so does effect. This concept has been demonstrated thousands of times in independent experiments. Conventional practitioners and homeopaths generally agree that the amount of active substance present in a homeopathic remedy is too small to have an effect on its own (this is why they can be marketed over the counter as harmless). For example, a 30C preparation (most preferred by Hahnemann) is a dilution equal to 1:10⁶⁰ . This dilution is equivalent to one molecule diluted in a sphere the size of the orbit of Neptune! Thus, high potency homeopathic remedies contain 100% vehicle and no active molecules.

Hahnemann felt that dilution increased potency only when the solution was dynamized. The process of succussion or trituration supposedly removes an essence from the diluent that is itself not lost during the dilution process. Two major problems:

This would imply that a solvent molecules could retain an imprinted memory of a dissolved molecule even after the solute molecule had been removed. This imprint or force would have to be somehow greatly magnified (rather than diluted) by the process of rapping the solution vial against a hard object since the original solvent molecules have also been diluted to near infinity. There is absolutely no independent empirical evidence for this; further these notions are contradicted by the evidence-based principles of physics, pharmacology and physiology.
Finally, why isn't the alcoholic solvent or the trace contaminants from the tubes, stoppers, and solvent dynamized during dilution and succussion?

On the positive side, a recent finding using certain organic molecules in polar solvents suggests that not all solutions behave classically and that in some cases dilution does not evenly disperse molecules. read about this research here.

Provings

Virtually none of the homeopathic remedies found in the Homeopathic Pharmacopoeia have actually undergone formal placebo-controlled clinical trials for specific diseases. Instead they rely on provings (the responses of healthy, cooperative individuals who take active doses (non-diluted) of a substance and report on its effects) to determine which diseases evoke symptoms similar to that seen in the proving. The substance tested in the proving is then prepared homeopathically and used in patients with the symptoms recorded during the proving. Many of the "provings" were conducted more than 150 years ago. There is no scientific validity to determining drug action in this way because:

The proving is highly subjective and is performed without regard to dose and other pharmacokinetic factors.
Like does not cure like.
The drug tested in the proving is not actually present in the homeopathic remedy anyway.

Scientific Validity

Efficacy