In this aphorism, Hahnemann states that in order to cure correctly, a physician must know three essential things:
- What is to be cured in the patient (the disease).
- What each medicine can do (the action or power of the remedy).
- How to apply the remedy properly (in correct dose, potency, and repetition).
The physician must study the disease thoroughly — not just by its name or pathology, but by observing the totality of symptoms, which are the true reflection of the inner disturbance in the vital force. Hahnemann emphasizes that symptoms are not separate from the disease — they are the disease itself, expressed externally.
He insists that the inner essence or nature of the disease must be “perceived,” not just seen. For example, if a patient has a tumor or diabetes, the focus should not just be on the tumor or sugar level, but on the unique symptoms and experiences of the person. Pathological changes may be irreversible, but functional disturbances (which appear as symptoms) are the real target of homeopathic treatment.
Hahnemann also points out that disease progresses from the center (mind/emotions) to the circumference (body). This shows the importance of understanding mental and general symptoms over just local or pathological ones. For epidemic diseases, Hahnemann recommends collecting and studying symptoms from many cases to build a complete disease picture — this leads to the selection of epidemic remedies, though treatment must still be individualized.
Finally, just as a disease must be studied from generals to particulars, so should the remedy. The drug picture is built by combining all proving symptoms from different individuals, understanding what is common and what is individual. This same approach was used by Hahnemann in identifying chronic miasms like psora, by observing thousands of symptoms and matching them to suitable remedies.
Thus, §3 teaches that successful healing requires deep knowledge, accurate observation, and correct application — all rooted in the understanding of symptoms, remedy actions, and individualization.