Homeopathy practitioners believe that imbalance in vital forces cause disease. Principles of Homeopathy were borne out of momentary delusion in the allopathic practitioner, Samuel Hahnemann.
Ayurveda practitioners believe that imbalance in body humors (doshas) cause disease. Principles of Ayurveda come from beliefs, religious texts and faith-healing and untested primal observations.
Naturopaths believe that short-term, acute illnesses are often the body’s way of clearing toxins and nature will eventually cure chronic illness. Principles of Naturopathy came to being because two guys were jobless in the 1800s and borrowed useless theories from herbalism and mysticism.
Chiropractors believe that the body’s nervous system acts as the conductor of "internal" forces and that bone misalignments that interfere with the transmission of innate forces causes diseases. Principles of Chiropractic came in a dream to its founder, who hallucinated that a ghost of a dead physician was talking to him.
If you consider these groups of people to be "medical doctors" then the joke is on you.