The enduring concept of the orders was fundamental to the perpetuation of the classical tradition, and it is central to much architectural theory. One of the most resoundingly influential of its elucidations was published in 1570 by Andrea Palladio (1508–80) in the opening book of his architectural treatise, the Quattro libri dell'architettura (Four Books of Architecture). There, as in other theoretical works from around this period and later, the five orders — Tuscan, Doric, Ionic, Corinthian and Composite — are presented as a hierarchy of purportedly ideal exemplars; and, in this particular case, their universal ‘principles’ (precetti) are conveyed through two sets of illustrations, one depicting colonnades (Fig. 1) and the other arcades (Fig. 2), together with many further plates showing various individual details. In each of the main illustrations, the specimen is given its own designated proportions of column-diameter to column-height, ranging from 1:7 for Tuscan to 1:10 for Composite, and a distinctive formal make-up for both the column and its accompanying entablature. What is little borne in mind, however, is that this published rendition of the orders dates from towards the end of Palladio's career and was preceded by three decades of prolific practice, during which time his approach — as we shall discover — was in many respects very similar. In other words, the Quattro libri treatment of the orders was not merely a necessary and predictable inclusion in such a publication, or just a theoretical or ‘paper’ exercise, which is rather how it has also been viewed, since, as we shall see, it was representative to a very substantial degree of Palladio's actual established practice and its underlying rationale and philosophy.