Through the Middle Ages building knowledge passed largely on site, from master to apprentice; the lodges that raised the cathedrals had no written theory. In the ten books he completed in 1452, Leon Battista Alberti set that knowledge down systematically for the first time: materials, foundations, proportion, the ordering of cities, repair.

Two ideas sit at the centre. The first is *lineamenta* — the linear order of a building, existing independently of its stones. For Alberti architecture resides not in the material but in that order, so the architect completes the design in the mind and on paper before a stone is cut. This distinction is the beginning of the modern definition of the profession, separating the architect from the craftsman. The second is *concinnitas*: the idea that beauty is the fitting together of parts such that nothing could be added or taken away — ornament is not applied afterwards, it is the proportion itself.

The façade of Santa Maria Novella is that theory applied: Alberti gave an existing Gothic church a face built on the proportions of the square and the circle, and used scrolled volutes to join two different heights — a solution copied for the next three centuries. The book was printed in 1486, after his death, and spread with the press; the treatises of Serlio, Vignola and Palladio continue the tradition. Architecture could be taught as a design discipline only once it could be written.