In science-based medicine, the term "subluxation" refers to an incomplete or partial dislocation of a joint, from the Latin luxare for 'dislocate'. While medical doctors use the term exclusively to refer to physical dislocations, Chiropractic founder D. D. Palmer imbued the word subluxation with a metaphysical and philosophical meaning drawn from pseudoscientific traditions such as Vitalism.
Palmer claimed that vertebral subluxations, interfered with the body's function and its inborn ability to heal itself. D. D. Palmer repudiated his earlier theory that vertebral subluxations caused pinched nerves in the intervertebral spaces in favor of subluxations causing altered nerve vibration, either too tense or too slack, affecting the tone (health) of the end organ. He qualified this by noting that knowledge of innate intelligence was not essential to the competent practice of chiropractic. This concept was later expanded upon by his son, B. J. Palmer, and was instrumental in providing the legal basis of differentiating chiropractic from conventional medicine. In 1910, D. D. Palmer theorized that the nervous system controlled health:
"Physiologists divide nerve-fibers, which form the nerves, into two classes, afferent and efferent. Impressions are made on the peripheral afferent fiber-endings; these create sensations that are transmitted to the center of the nervous system. Efferent nerve-fibers carry impulses out from the center to their endings. Most of these go to muscles and are therefore called motor impulses; some are secretory and enter glands; a portion are inhibitory, their function being to restrain secretion. Thus, nerves carry impulses outward and sensations inward. The activity of these nerves, or rather their fibers, may become excited or allayed by impingement, the result being a modification of functionality – too much or not enough action – which is disease."