Our bodies are actually built to heal itself. But because we are also made up of Mind, Energy and Soul (aside from our physical body), the complexity of our nature sometimes leads to a breakdown of sorts, which results in disease and sickness. The root of "disease" afterall, is dis-ease or disharmony in our system. When a breakdown happens, a third-party expert (detached from the subjective experience of the disease) is generally better equiped to channel and administer the skills required to realign the body to health.
The healer serves as a conduit for the Divine, the cosmic forces or energies needed for the healing to happen. While there are people who can actually heal themselves (Yogis, Masters), most people are not yet in that stage of development where they can regulate their own spiritual, mental and soul bodies -- It is like performing surgery on your own body (difficult but certainly possible). It is also the reason why no one healer can cure all diseases. We are still in an evolutionary stage where we still need one another.
Each healer has a specialty. Medical doctors specialize on the physical, psychiatrist and therapists treat the mind, priest/rabbis/monks deal with the soul, while shamans and energy practitioners channel energy. Traditional healers and medicine people generally specialize in either the mental, soul or energy (spirit) bodies, but many practitioners combine all three, as well as offer traditional massage and herbal therapy to realign the body too. No one has a monopoly on health. It is therefore vital that healers cooperate with one another to give the patient the best possible care. But without exception, the source and drive of all healing comes from the Divine (God) -- the deepest part of ourselves inside and out, where our "being" and the Cosmos unite.
We are truely one with God. But our physicality deceives our minds and makes us believe that we are limited and localized within our bodies. God surrounds us and permeates every cell in our bodies. God is Chi, God is Prana, God is all science, God is the Cosmic Mind. These things are united as one, with all the known forces in the Universe and beyond. We are more than our bodies, and this reality makes it possible for us to heal. The only service the healer (no matter what type) does, is to realign us back into unity with the Divine. The Divine is always present and available to anyone, it is our own nature and distorted perspectives that misaligns our system and causes disease.
