Healing can mean many things. Sometimes it means simply being free from troublesome symptoms. Sometimes it means returning to a higher state health or vitality in addition to symptom relief.
It seems like a basic question, but there are different ways that healing modalities work, and the distinction really matters. Many pharmaceutical drugs work strongly to control discrete disease processes, like putting a specific chemical key into a lock to get it to turn. Sometimes that works with the body's own mechanisms, sometimes it overrides them. If it is a very strong disease process, it can be important to powerfully override the biochemical terrain to protect the integrity of the system - think of using steroids during a severe inflammatory reaction, epinephrine during an acute allergic attack, or strong antibiotics for a septic condition to prevent tissue destruction and organ failure.
In these cases, the medicine given is doing a job for the body. Normal functioning is compromised, so the medicine is jumping in to correct it. When medicine is functioning this way, it will only continue to work when it stays at a particular dosage level in the bloodstream, which is just another way of saying that the chemicals need to be in adequate concentration to do their job. Once they exit the system, dysfunction may return, since the medicine was forcing the system into a particular pattern of function that may or may not hold. This can be true of pharmaceutical medicines, but also herbal medicines as well. It can also be true of surgery, where we may go in to change the structure of something anatomically, which may be corrective in a structural way, with varying degrees of success in changing the function of the system.
For all these therapies, we might call this effect of pushing the system physically or chemically in one direction the primary therapeutic effect. However, there is another very important way therapies can interact with the system. Different medicines and manual therapies can have a stimulatory effect on the system - they cause the system to react in a particular way, that is fundamentally different than a chemical interrupting a biochemical process in the body. An excellent example might be using an herb like coptis or goldenseal, which is very bitter and contains compounds like berberine. If you took a tincture of one of these and held it in your mouth, the taste and nature of these herbs, quite instantaneously, would stimulate the activity of the solar plexus and the liver-gallbladder system, without any of the chemicals in those herbs physically reaching those areas.
This is an important notion - that a substance or therapy can talk to the system and elicit a reaction, without having to override the biochemical functioning of the system. We can call this the secondary therapeutic effect. What is so importance about this distinction? The secondary effect is the body's own homeostatic response, as opposed to the effect of the medicine itself. The primary effect is only helpful as long as it is continually influencing the system, and often wears off when it is taken away. Stimulating the body's own functional response, if done properly, restores correct functioning that has been lost due to stress, aging, or insults to the system.
If possible, it is always, in every way, better to restore functioning to the system than to administer a medicine to force the body to stay in balance. There are many reasons for this, not the least of which is that anything that is forcing the system back into balance will gradually become less effective over time, or produce greater and greater side effects and further lack of functioning. Restoring correct functioning increases vitality, corrects the root of the illness, and also prevents further illness progression and complications.
Usually the medicines and therapies that elicit a secondary effect are gentle, since they are working in the same direction as the healing response in the body, but this also means that they take longer to work, and the results aren't always dramatic in the beginning. However, once proper functioning has been restored the results are always longer lasting, and not dependent on the continual need for strong medicines to keep the body in balance.
These principals of primary and secondary effects can be seen across a number of therapies. In drug therapy, it can be dose dependent - low-dose naltrexone has a stimulative effect on receptors, in ways that larger doses do not. We see this across herbs, and homeopathic remedies as well - oftentimes the smaller the dose (especially when it is potentized), the more the secondary effect is emphasized. The higher the dose, the closer we are to a toxic dose, and the greater the side effects.
The intelligent practitioner deftly uses therapeutic tools, whether they are medicines, manual therapies, acupuncture, psychotherapy, etc - to restore correct functioning, not merely introduce a crutch to compensate for a lack of proper function, which will eventually need more and more support to prop up.