Pathogenesis is the exaltation of an individuality, not in time or in space, but in its totality. You can read the pathogenesis of a remedy and observe feelings, fears, dreams, sensations –a way of perceiving and living life. If we understand this correctly, we understand that the simillimum is invariable; it does not change during the whole life of the individual. When you administer the simillimum, the remedy as well as the potency, the picture changes, naturally, we are witnessing the cure. But cure does not mean to remain in a state of grace for ever. It is a path, a road of development, of growth, with psora in a slumbering state, thus not precluding being. The human being does not stop being susceptible, his vital force, even when balanced, remains susceptible to become unbalanced. The simillimum does not force us to be anything but humans, human beings susceptible to falling ill. And because of that, new situations arise which call for prescribing. As you said, we have the influence of many external factors, but they are external factors which the subject will resolve better with his simillimum than with any other remedy. An Argentinean doctor noted, in a course which I took, that a female patient who was taking her simillimum was involved in a car accident, and she suffered a big open gush in the forehead. Besides the emergency care she received at the hospital, she was given Arnica, and some other remedy to help her get over the consequences of the accident. The wound closed completely, but after a few years –note, years! - the patient started to take again her simillimum. Up to then, because of the misperception of her homeopath, she was taking similar remedies for this or that, but she had not been given her simillimum again. Well, the patient recovered her general balance and, in that thrust toward the integral cure, which only the simillimum can unleash, the scar from the accident wound in her forehead reopened –forming later a new scar, this time in a natural and permanent way. This example, which is a real pearl of wisdom, shows us that the simillimum is one for our whole life, and that any remedy which is not the simillimum is a suppressor, even if it does not cause so much suppressive damage as allopathy can produce.
The simillimum is a remedy capable of rebalancing the Vital Force of a human being in his or her totality. Any of our remedies, when studied in depth, has phases of expression. Remedies present a psoric, syphilitic or sycotic face, according to the phases of imbalance through which the human being is coursing, but the remedy which connects with his Vital Energy in its totality is one and the same for his whole life. But, of course, I am aware that this is an ideal situation.
I understand that, in his daily practice, the homeopath has to proceed by successive approximations, because, in the end result, the prescription has to be arrived at through the presenting symptoms of the patient, and these symptoms change. But a deep understanding of disease, and thus of how the human being lives that imbalance which precludes him from being what he has to be, and an in-depth understanding of the remedies --not through the symptoms which they manifest, but through that exalted individuality that has been displayed in the healthy human being, in the peculiar mode of suffering, of being impacted by the events of life, etc.--, a profound understanding of these issues--note the emphasis--, will lead us to see that the simillimum is one and invariable during the whole life of the person, and that the job of the homeopath guided by the highest ideal of cure at this level is to find that simillimum.
You know that it is not possible that, after receiving the correct remedy, the patient would develop a more serious disease than the one he came to get treatment for. This is so because, were it to happen, it would only prove that he has suffered a suppression, and that, consequently, he did not receive the correct remedy, but a suppressive one. If, on the contrary, the disease that appears after administration of the simillimum were to be less serious, we would know that we are on the path to cure, and it would not be advisable to interfere with its course through the administration of new remedies. The simillimum will bring resolution; it will reopen the path of balance in the person in any circumstance, acute or chronic. The acute picture, when correctly understood is the exaltation of the chronic picture of the patient. The problem is that it is extremely difficult to find that simillimum, and that we have to admit, with the greatest humility, that in our daily practice we resort mostly to polycrests because our knowledge of Materia Medica is quite limited, and this leads us inevitably to a shortcoming in the level of individualization which homeopathy proclaims. Often times we don’t have a choice, but, as I believe I have mentioned before, the difference is to be aware of the fact that we are resorting to similars, and to remember that the simillimum is a quest toward the ideal, a search which I personally think that we cannot afford to give up.