Dalla citt\ue0 per parti alla citt\ue0 per layers

In the past century the schools of urban studies would work onto the common ground theory of the city of parts that is here assumed as what germinated from the seeds that Aldo Rossi sowed. Starting from the last third of the past century, the pulverized urbanization of territories has sparked off a progressive and pressing phenomenon of loss of control of the form that is suddenly no longer a finite figure. The inexorable increase of weakness of the bijective links between architectural, urban and landscape elements, along with the loss of homogeneity, reiteration, density and continuity that characterized the finite parts of the city, undermine the possibility of going on working according to the paradigm of the city of parts. The shift from unity to multiplicity implies the availability to new, and not foreseen nor expected, landscape relationships: from the closed to the open, from the whole to the fragment, from the finite to the infinite, from the commensurable to the incommensurable. The issue of the loss of form as a finite figure, and furthermore, the one of the loss of the power to control the form of the extensive city appears analogous to and interlaces with the issue of bigness. The city, as well as architecture, loses its boundaries, and the commensurability between its parts and the whole fades. Sharp urban boundaries can no longer be drawn. The architecture of the city is no longer supposed to delimit a boundary, the perimeter of a finite figure, but becomes rather a fragment, a finite edge capable of measuring and describing the infinite. The dialectics between finite fragments and extensive matter is now very different from what is was according to the classical art of composition, where the architectural and urban matter would be shaped by drawing, into a finite figure, which was structured along the principle of concinnitas between the parts and the whole. In the extensive city, the bijective relationship between form and matter cannot find the former conditions of finiteness and commensurability. The discontinuous and rarefied drawn form, which clots into solid concretions, is a counterpoint to the undrawn matter that liquidly spreads out according to its intrinsic formal logic, escaping the classical orders. This double articulation of the formal systems, referable to the rationality of drawing and to the apparent chaos of matter, suggests, as a free association of ideas, a paraphrase of the subdivision of reality into res cogitans and res extensa, which is obviously unfaithful to the Cartesian paradigm. The architectures of the city are cosmetic fragments, logical propositions, regulating devices that are capable to partially support the extensive matter, without containing or wrapping it, and leaving it to flow through their weakness and their fractures that allow them to be versatile segments of the construction of an ever-evolving discourse on landscape. Rather than through finite parts, the extensive city can be described through a complex and not univocal combination of multi-positional, multi-directional and multi-dimensional layers. The res extensa, matter endowed of its own intrinsic formal structures, deploys onto layers. The drawn cosmetic fragments can work as captions or tidy concretions of the matter itself, or as sections as well as intersections of different layers, intelligible dots or lines, capable to describe, explain and measure the indefinite res extensa. The aesthetic of intelligibility blends in the aesthetic of sense; geometry and passions contaminate and support each other. The layers where form and matter stratify and intersect, are relational formal structures with different levels of ephemerality, which can be continuously manipulated by shifting elements from one layer to the next. The layers of contemporary city, unlike the archaeological layers, are not diachronically overlapped, but synchronically interlaced, multi-directional and multi-versal spatial intersections, disappearing and reappearing, continuously blending into each other