Chiropractic is generally categorized as complementary and alternative medicine (CAM), which focuses on manipulation of the musculoskeletal system, especially the spine. Its founder, D. D. Palmer, called it "a science of healing without drugs".
Chiropractic's origins lie in the folk medicine of bonesetting, and as it evolved it incorporated vitalism, spiritual inspiration and rationalism. Its early philosophy was based on deduction from irrefutable doctrine, which helped distinguish chiropractic from medicine, provided it with legal and political defenses against claims of practicing medicine without a license, and allowed chiropractors to establish themselves as an autonomous profession. This "straight" philosophy, taught to generations of chiropractors, rejects the inferential reasoning of the scientific method, and relies on deductions from vitalistic first principles rather than on the materialism of science. However, most practitioners tend to incorporate scientific research into chiropractic, and most practitioners are "mixers" who attempt to combine the materialistic reductionism of science with the metaphysics of their predecessors and with the holistic paradigm of wellness. A 2008 commentary proposed that chiropractic actively divorce itself from the straight philosophy as part of a campaign to eliminate untestable dogma and engage in critical thinking and evidence-based research.