Of Celsus’ Artes (early first century AD), which originally handled agriculture, medicine, the art of war, rhetoric, and philosophy, only the eight books on medicine survive. Celsus’ work attests to the vibrant interdisciplinary culture of the early Imperial artes. The books De medicina in particular reveal a distinctive conceptualization of specialized knowledge that bears the hallmarks of the scientific culture of the artes but contrasts sharply with the approaches of Vitruvius and Columella. Celsus’ theory of the medical ars self-consciously appropriates but also develops and expands key methodological terms from the Greek medical tradition, including reason, experience, cause, and nature. These terms set the parameters for Celsus’ exposition of medicine, as exemplified in discussions of bloodletting, fevers, and fractures. Celsus’ more reserved attitude toward the kind of knowledge of nature required for expertise does not ignore the central preoccupations of the scientific culture of the artes, but instead pragmatically inflects them for medical practice.