Early modern architecture has often been regarded as a composition of simple volumes coordinated by the mathematical proportions of the ancient classical orders. There is yet a third prominent feature besides geometry and orders to consider, the vaulted structures. Thus the volumes of architecture are not incorporeal as those painted by the perspective artists, but are shaped by walls, vaults and domes. Form and statics were questions that Renaissance and Baroque architects could not even separate, firstly for physical reasons: in an unreinforced masonry building, a formal choice has always static consequences on the arrangement of the structural bodies; and, vice versa, the adoption of a static device conditions the layout and appearance of spaces. Static invention always contained a formal component, and the architect’s main task was the tridimensional configuration of geometric volumes and structural walls; or – in other words – the setting of equilibrated masonry bodies that gave shape to the architectural spaces. This act was purely intellectual, not only technical or practical, and preceded any other choice about the building techniques, site management, or materials. Nevertheless, the scholarly literature usually separates structural from artistic genius and the study of construction knowledge has been approached mostly either by the fields of structural engineering or the history of building technique, and sometimes by the history of science. Recently studies in the latter have been trying to argue that the Renaissance major achievements were linked to the development of modern science and philosophy. Although fascinating, this idea may be misleading: I wish to show that early modern builders possessed knowledge of statics of their own, entirely different from either ours or that of Galileo, and that it must be examinated iuxta propria principia, that is according to the actual horizons of thought in which it had been developing. In short, we need to reconstruct what Michel Foucault defined as an “épistème,” a system of knowledge that allows, within a particular epoch and culture, to develop only some concepts and not others. Early modern invention, in the domain of statics, followed a proper set of rules grounded on the basic principle inherited from antiquity and the Middle Ages: the imitation of Nature and its divine laws established by the Creator. The first means of Renaissance and Baroque statics were of course the mathematical arts, but the early modern men had a completely different idea from ours of those disciplines: rather than sciences, geometry and arithmetic were conceived of as operative skills, reduced to a set of simple empirical prescriptions in which the visual aspect always prevailed over mathematical demonstrations. Geometry, arithmetic, the principle of authority, and intuitive observation of the behaviour of natural or man-made structures, were joined together into a body of knowledge that grounded formal-static invention. Nontheless, being the masters unable to separate statics from dynamics, the strengths were considered kinematic mechanisms, so that every structure was conceived as a dynamic equilibrium of small movements within the masonry that had to be prevented and opposed. The terms used to explain structural behavior at the time are quite meaningful: “the arch never sleeps” said the Arabs, while according to the Italian masters the “violenza delle volte” (the violent thrust of vaults) generates some “motivi” (small movements), which should be firmly stopped by the “contrasti” (oppositions, restraints), in order to make the structure “stare ferma” (stand still).