Dr. Bradford tells us that at the time of Hahnemann's translation of Cullen's 'Materia Medics,' that is, at the beginning of his in dependent investigations in 1790, he had no preconceived theories or opinions to sustain. This view of his biographer is corroborated by the absence from Hahnemann's writings of even remote reference to any a priori concep tion or suspicion of a general curative relation between drugs and diseases. Nor does it ap pear that he then possessed the faintest con ception of the magnitude, or of the quality, of the task he was gradually assuming. His orig inal object evidently was to ascertain why Peruvian bark cures intermittent fever, and to learn if the view held by Cullen — that its curative property resides in a combination of bitter (tonic) and astringent qualities— was indeed true. There is no historic evidence that before 1790 the general therapeutic principle of similars had even dawned upon his mind. But we may be sure that the logical and philosophical principles that must necessarily govern his researches had been well thought out before the work had very far advanced.
Hahnemann and his disciples claim that in the discovery of homoeopathy as a general prin ciple of organic science, and in its conception and development as a system of medicine, as sumption, speculation and hypothesis have had no place; but that observation, experimentation and inductive classification constitute the scien tific and solid foundation of fact upon which it rests. They assert that all its essential doc trines are susceptible of demonstration, that they have been verified and reverified times without number, and that for the first time in the history of intellectual development the estab lishment of the homoeopathic principle showed that the Baconian method of research is as applicable in the realm of therapeutics as in any other department of scientific investigation. If we look over the records of the processes leading to its discovery, it appears that these processes were under the guidance of the fol lowing principles of scientific philosophy, all of which are distinctly set forth by Hahnemann in his (Organon' : (1) That in the study of disease with a view to its cure, the only safe dependence is upon the manifestations (symp toms) perceptible to the senses, and that no safe conclusions can be drawn from mere theories erected upon these signs and symptoms. The signs and symptoms constitute the only side of the disease that is turned toward the physician, and the totality of these signs fur nishes the only true expression or portrait of the disease; (2) that the specifically curative power of a drug resides not in its physical, nor yet in its chemical properties, but in its capac ity to produce changes in the functions of the organism; (3) that the dynamic properties of a drug—in other words, its power to specific ally cure disease — can be ascertained only by observing the signs and symptoms which it can produce in the organism, and that these specific ally curative properties cannot be inferred from the physical or chemical properties of the drug substance; (4) that experiments for the pur pose of ascertaining the pathogenetic properties (signs and symptoms) of drugs must be con ducted under the precautions necessary in other researches; and the tests must be repeated and varied with a view to eliminating every influ ence and agency that can vitiate the experiment.
The drug experimented with, and the person experimented upon, must both be °standard.* That is, the drug must be pure and unmixed with any other substance capable of disguising, modifying, or otherwise affecting its own spe cific activity, and the person experimented upon (prover) must be possessed of good health, and free from any unhealthful occupation or habit, and from any mental, moral or other influence or agent that modify the pure effects of the drug upon his organism. Also, that the experimentation with the drug must be con tinued until its whole pathogenetic effect has been elicited; (5) that the observations made from such experiments as those here indicated constitute the only source of a pure and °stand ard* materia medica, and supply the only ma terial from which general therapeutic principles can be discovered or deduced; (6) that ef fects observed from the action of a drug upon diseased persons (clinical effects) or those ob tained from a combination of drugs (polyphar macy) are not "standard" effects and cannot serve as reliable guides in a search for thera peutic principles.
In the opening sections of the Hahnemann mentions as among the physician's essential acquirements: (1) Knowledge of disease; (2) knowledge of the dynamic prop erties of drugs; (3) knowledge of the curative relations between the two. This knowledge he holds essential both to the development of thera peutic science and to enable the physician to prescribe the curative remedy. In order to qualify the physician for his work his knowl edge of disease must be composed of facts perceptible to the senses. Our physiological and pathological deductions in reference to a case of disease are more or less uncertain and theoretical. Absolute knowledge of disease is limited to its signs and symptoms, besides which there can he no certain and assured foundation for a science of therapeutics. The knowledge of drug-properties must be equally certain and substantial. All drugs possess three classes of properties — physical, chemical, and specific or °dynamic.* The physical and chemical proper ties can be ascertained by physical and chemical methods. The specific or dynamic properties, that is, the properties which alone impart the power to accomplish specific cures of disease, can be learned only by observing their power to cause changes in the health of the organism as shown by their capacity to produce signs and symptoms. Here again the signs and symptoms constitute the only sure basis of classification and induction in the construction of a science of therapeutics.