Claude Perrault, a founding member of the Académie des sciences and architect of the Louvre, is a figure emblematic of architecture’s transformation by the so-called scientific revolution, representing a radical break with tradition. This article will address Perrault’s scientific challenge to architecture as one that harks back to both ancient and modern sources. It explores some ways in which Perrault integrated the analogy between medicine and architecture into his approach to this art and assimilated medical concepts, particularly observation, into an (...) empirical medical approach. This notion of observation was at the heart of the practical aspect of ancient philosophy as a care of the soul which articulated the ancient comparison of the charismatic orator to a doctor. Thus, Perrault’s remarks on Vitruvius’s authority can be broadened beyond architecture to the quest for a guide to living, transcending disciplinary boundaries between natural science and art. Further, Perrault’s claims for naturalness in observation share a double perspective: observation as a new form of learned experience reflects the ethos of the scientist, while, as a traditional activity of peasants, it reflects a raw empirical knowledge about rules of life condensed into habit and custom, enabling common people to be the physicians of themselves. (shrink)