Modern medicine tends to privilege disciplines promising "objective" laws governing body parts (from molecules to organs). Studies on a person's illness and disability are (apparently) confined to "subjectivity." The Specialty of Physical and Rehabilitation Medicine is often regarded as a humanitarian approach, belonging at best to the family of "soft," "qualitative," or "quasi-experimental" sciences. This specialty often claims specificity by labelling itself as "functional" and "holistic." However, it is shown here that the former term is acceptable, yet redundant, and the second misleading. When human behaviors and perceptions are at stake, "function" indicates a person's relationship with the outer world (already tackled by the definitional term "physical" from the Greek "physis"). The word "holistic" emphasizes mind-body unity and person-environment interdependence but, in current usage, overshadows the complementary need for an analytic, experimental approach to any function. Medicine aims at fighting disease and disability in single persons. This endeavor requires knowing body parts and mechanisms and understanding how interventions on "parts" affect the "whole." This understanding rests on the experimental method. For instance, returning to a given societal role (participation) may require restoration of walking (activity), which may require reinforcement of weakened muscular groups (impairment). Working only on holistic bio-psycho-social "wholes" may miss the therapeutic mission of medicine.