Caramuel’s Architectura civil recta y obliqua is a treatise in which architectural order is tested precisely where geometry ceases to remain orthogonal. Its sections on inclined surfaces, oblique architecture and the species of obliquity examine how straight rules generate transformed delineations under altered spatial conditions. Obliquity is therefore not presented as an escape from geometry but as a demand for a more exact geometry. The iconic operation is rule mutation: a system proves its strength by remaining intelligible when orientation, projection or inclination changes. This is particularly important because the treatise treats deviation as something that can be described, classified and constructed rather than as an exceptional failure of the norm. The theoretical contribution is an architecture of conditional rules. Form is no longer secured by repeating a canonical figure unchanged; it emerges from the disciplined transformation of relations. The wider bridge is to parametric reasoning, transformation grammars and adaptive systems, in