According to Rossi, the theory of composition developed by the French master in the essay by late eighteenth century, summarizes two characters of absolute validity and modernity: the construction of a logical process of investigation of forms, therefore, the will to establish, within the act project, the primacy of conceptual moment on operational moment. In the first aspect Rossi get confirmed of that rigorous scientific attitude, that commitment, that he developed since 1964 when he was appointed professor of the course "Distributive features of buildings" at the School of Architecture of the Polytechnic of Milan, aimed at working out a theory of design as rational and autonomous explanation on how to proceed in the practice of the trade. Autonomous, that is, all internal to architecture itself because developed from, and in the sense of, form. On the other hand, the distinction between the theoretical moment of conception and the constructed work, as well as establish the primacy of knowledge on doing, illuminates a continuous tension between rational construction and subjective contribution of the architect, claiming a decisive importance to autobiographical expression.

A prospect that Rossi summed up in the definition of “authentic rationalism" and propose to the public of professionals like the attitude that alone can lead to an improvement of architecture and of its construction, offering itself like an alternative both to the controversial legacy of the Modern Movement, and to the most barrens and arbitraries researches undertaken by the national architectural culture after the Second World War.

The comparison establishes by Rossi with Boullée in the few pages of the Introduction, it has been repeatedly brought to the attention of critics (C. Olmo 1986, A. Ferlenga 2005, A. Vidler 2008), often presented as an occasion in which the Milan architect faces and develops some of the main themes of his poetry. However, it still doesn’t seem to have been started a complete in-depth study of the relevant density and complexity of the messages included in Rossi’s text, whether they are developed, suggested in an indirect way or only prefixed by the author. As a matter of fact, the translation of the French manuscript fit in a short time’s span (1966 - 1970) marked by the working out of the most significant writing of Rossi, a very intense production witnesses to the ripening of interest built up over time: from Enlightenment heritage, to the need of construct a logical and rational system of architecture, until the resolution of the relationship with the history with the definition of a line of research, a "tendenza”, of which we trace the contributions in tradition, Boullée itself, and of which stubbornly we continues the thread of experience.

Against a large productiolished works, personal notes, correspondencnts, or even university lectures, the research herethe productionings as only source and main tool for interetics between 1954 and 1967. The most important attemthe machitectural references, as well as the orign in time of the themes and key terms that convergn ofalism" as presented in the Introduction of 19analysis was completed and accompanied by the study of twork, both subsequently revised and published: the first, I Nuovi Maestri. Architetti tra politica e cultura nel dopoguerra, (Giovanni , focuses on the reconst routl strategies put in place, in the first years of critical training (1954-1958), by Aldo Rossi and a group of architects identified within the chronological limits between 1923 and 1932, the second, Aldo Rossi e L’architettura della città (Elisabetta Vasumi Roveri 2010), evaluates the vast production of writings - published or not - that have preceded the writing of Rossi's first book. An analysis of the process of writing the text in order to reconstruct its maturation over time by not isolating experiences, activities and readings that intertwine and overlap with it.

The first chapter, Concept of tradition and appeal to realism, it is proposed to summarize the context, the places and the personalities that have been in charge and that have characterized the debate on tradition in architecture, almost exclusive protagonist of Rossi’s formation. In addition to being one of the first issues faced, the relationship of the discipline with the history of itself will accompany the thought of the young student in all its subsequent development, defining the comparison with some important masters of the past (Claude N. Ledoux, Jean N.L. Durand, Giovanni Anthonio Antolini, Alessandro Antonelli, Adolf Loos), until been confirmed as a matter solver, even as instrument itself, of the attempt to re-found architectural profession.

In the Italy of the economic miracle, of the student associations, of the thriving cultural and architectural journalism and, above all, of the strong presence of communist ideology, the School of Architecture are no longer considered as opportunities for intellectual education, encouraging the development of alternative forms. The House of Culture, the Movement Architectural Studies, the International Union of Students, but also magazines such as «Il Contemporaneo», «Società» and, especially, «Casabella-Continuità» directed by Ernesto Nathan Rogers, are the true stage of comparison, criticism and creation of new values that presides over the formation of Rossi.

With the convention of 1954, Modern architecture and national traditions, Rossi is confronted for the first time with the term “tradition” in architecture; associating to it concepts such as "responsibility", "morality" and "historical consciousness", he develops, together with Carlo Aymonino and Francesco Tentori, a first definition completely aimed between the will to take a position with respect to the debated legacy of Modern Movement, the main themes of Rogers’ teaching and the echo of the cultural policy of the PCI as defined by Togliatti and Alicata. After the subsequent controversy triggered by Giancarlo de Carlo in the pages of «Casabella-Continuità», addressed to a group of students of the School of Architecture of Milan, Rossi develops a series of articles, in particular in collaboration with Guido Canella, in which he appropriates of critical tools and argumentative strategies taken from literary and cinematic, leading the reflection on the concept of tradition to the more general question that grips young professionals: the renovation of architectural language, finally arriving at an initial proposal specification. The proposal of a "realist architecture."

First step towards a linguistic definition, dealing only with the article “The concept of tradition in neoclassical Milanese architecture”, published on «Società» in June 1956. In this paper, the deepening of the concept of tradition, begun at the conference of '54, as well as the following argument for a "realist architecture", find their first formulation in the reading that Rossi offers of Neoclassical architecture in Milan. A reading that succeeds both in legitimizes a theoretical position but also that advances a definition of terms more properly linguistic of the architecture so-called realist. The concepts presented above of "responsibility", "morality" and "historical consciousness", traced to a single attitude of rationality, are specified on the one hand in the criteria of simplicity and prmmitment to the practical purpose and to the new tasks that society expressed (Giuseppe Piermarini), on the other hand the ability to convey, in the understanding of the meanings of the forms belonging to the tradition, the new political ideals and morals of society (Luigi Cagnola).

For Rossi, professional consciousness and historical consciousness are two aspects of the same ratio that should govern the construction of architecture as much as that of the city.

The reference to neoclassical architecture, but especially to the characters of modernity that Rossi found in this period of history of architecture, has a crucial debt, besides the positions of some activists historians and philosophers members of the intellectual elite of Milan, to the researches carried out by Emil Kaufmann on the French architecture of late eighteenth century. Comparison with historiography. The methodological contribution of Emil Kaufmann, it is proposed, beginning from an analysis of his education at the School of Vienna and a well-established critical analysis of his work (M. Shapiro 1936, G. Teyssot 1981, C.S. Wood 2000, A. Vidler 2008), to identify the main criteria and methods of historiographical interpretation developed from the Viennese historic, therefore, how their reflected in the writings of Rossi.

In communion with the researches conducted by young historians gathered in the New Viennese School - including Hans Sedlmayr and Otto Pacht - Kaufmann’s analysis are addressed in a special way to the principles underlying styles and to their development, allowing to consider the work of art as a complex structure in which different aspects of reality relate and organize into a whole. However, beyond the autonomy of the a priori formalist method and away from the development of a relationship between society and culture, resuming that between structure and superstructure upon which is based historical materialism, the model developed by Kaufmann, in establishing a homology between different fields - economics, social sciences, philosophy, as well as history -, introduces a new complexity in the interpretative structure of the work of art, continuously commensurate with the developments of thought and culture.

The figure of Ledoux, presented as a spokesman for a new idealism based on reformed horizons of morality and law, fully responds to Rossi’s calls for a renewed architect's social responsibility towards his work. A professional commitment that if on one side is characterized by the will of represent, respond and adhere to its own time, on the other hand is resolved in the definition of an autonomous figurative system, ceaselessly striving to elevate the form to new meanings, to the "new culture".

The definition of rationality in architecture, which Rossi developed from the first reflections on the concept of tradition, as consciousness both civil, referred to the needs and ideals of the present time, then historical, that is the formal repertoire of tradition and its belonging to a culture and to a consummate experience ended in the past, it is proposed, in the late fifties, as a response to the controversial search for new figurative paths. In the chapter Searching for a new figurative language: invention or creation?, that include the articles published in «Casabella-Continuità» between 1955 and 1958, Rossi is confronted with the attempts, made especially by young architects his peers, to investigate new approaches to architectural form, from technical innovations to the return to the materials of traditional environment. Therefore, need for experimentation, for original expression, but difficulty to clash with the indissoluble relationship between ethics and aesthetics built by the Modern Movement, together with the unstoppable rationalization and expansion of the production process and the fear to translate a possible confrontation with the ancient cultural and architectural heritage in a fruitless formal inventory.

"Continuity or crisis?"

Look to history but creative s aimed at the future, continuity as the original and conscious combination reaching for a definition of modernity that does not exist a priori but that, precisely in the historicity in which it is expressed, derives its definition; this Rossi’s answer. Following the research conducted by François Calì on Greek temple, the Milanese architect reflects on the concept of a monument for classic architecture, of symmetry as a symbolic moment stretched between the representation of the raison d'etre of the work and the work itself, finding in the definition of Technique the synthesis of the relationship between rational moment of theoretical investigation and contingency of the creative and original aspect of the single realization. According to this dialectic, which is necessary, form avoids the danger of fixity and abstraction obliging themselves to a new temporal perspective: continuity with a past that is memory, which is ahistorical validity of the principles and meanings places by reason, and renewal in the interaction with the possible forms of the present. A meditation on the persistent forms that reports the historical dimension in the foreground.

According to Rossi, from the moment in which the problems of architecture are recognized as immutable, becomes essential to verify, in history, the architectural forms that have already been able to resolve in itself the complexity of a design rationality renewed in places and techniques, therefore, in the singular will of the artist. The particular choice of some masters allows Rossi to define a line of research, to deepen a subject of which he can trace the contributions in the past and of which he decide to stubbornly bring forward the thread of experience: Boullée, as well as Adolf Loos and Le Corbusier, is at this point presented by Rossi as an interpreter of that "authentic rationalism", of that "tendency" of which he wants to convey in the present. The next two chapters, Rationalism exalted, a response for a new disciplinary foundation and The Boullée’s compositional system as an instrument of modernity, after a brief reference to analyzes conducted by Rossi on modern masters, finally addressing the terms of the comparison with the Essay on Art. The description of the compositional system developed by the French master, the issue of the teaching of design, the reflection on the term “invention” and on the temporal dimension of the architectural work, is woven into the Rossi’s discourse solving, in an autonomous disciplinary position, issues open since the early years of its formation.