Many believe that one of the fundamental characteristics that distinguishes our era from preceding ones is the diffuse nature of knowledge: a multiplicity of specialized disciplines, the result of an increasingly marked division of labor and a multiplicity of subjects, each endowed with its own experience, identity and irreducible autonomy, and very specific body of knowledge. The division of labor and the progressive democratization of western society over the course of the entire twentieth century, and especially during its last years, have allowed diffuse thought to emerge contrasting with the unitary and dominant thought of the preceding eras. In this regard, the city and the construction of its project, using the term in it broadest sense, are particularly interesting areas for observation.

The construction of a project and policy for the city has become, in recent years, an open field of inquiry. I use these words in Pierre Bourdieu's sense to point out an area in which many subjects, with different expertise and experience, different histories and cultural backgrounds, interests and powers, bonds and relationships with the rest of society are allowed to express their interpretations and proposals. This has obviously allowed us to understand the unexpected intersections of apparently distant bodies of knowledge and to create new and interactive constellations of knowledge. It has also allowed many individuals or groups to unearth knowledge that was once buried. One of the results has been the expansion and dispersion of the languages through which these subjects represent themselves and the ensuing practices that take shape.
The urbanist, like other researchers, faces the diffusion and dispersion of knowledge on two principal, and often intersecting, occasions. On the one hand, in the continuous and necessary confrontation of ever more numerous, specialized and exclusive fields of study with expert knowledge that, by invading the traditional field of study, erodes its identity. On the other, urbanists face this phenomenon in the continuous and equally necessary encounters with administrators and citizens who unite in various ways, often resorting to knowledge that is misunderstood, banalized and reduced to mere rhetoric, in fact, obscuring the knowledge of which they could be its unique bearers; that is the specific relationship with the state of things, with the characteristics of the city or the territory to which they refer from experience.
I have a certain experience with these things. In what is now my long life as an academic and planner, I have promoted and participated in innumerable formal and informal meetings, both spontaneous and planned, with the citizens and the inhabitants of the areas that became the material of my studies and projects. I have met with representatives of specific categories, groups and associations, with administrators and officials, as well as with academics from other disciplines. With them, I sought to understand the different situations that were presented to me; to build strategies, policy and concrete projects; to redefine objectives; to grasp the convergent, incompatible or incongruous aspects lying within the various requests, proposals and issues that were put forward; to compose scenarios as possible points of retreat, evaluating the costs and presumed benefits of every action, strategy, project and policy.
In many cases, there were meetings in which the roles of the participants were clearly defined; in others there were walks, site visits and seminars in which roles intermingled or, at least, were not rigidly ritualized. Such meetings are important occasions for a planner - as long as he or she knows how to recognize and to reflect at three inextricably linked levels. The first is a superficial level usually concerning the proposal or request itself; the second regards the arguments used to substantiate the proposals and requests; and the third involves the language and the discursive forms through which requests, proposals and issues are formulated. Each of these levels is guided, and acted upon, by concrete subjects, with concrete biographies and positions - real or imaginary - within a local society. It seems difficult to me to think about diffuse knowledge without stating clearly where and how it can be understood.

Those, for instance, who approach these occasions and events in the hope of gleaning the common knowledge distributed throughout society, constructed by experience over time and in contrast to expert knowledge, are usually disappointed. It is often the very groups and individuals with little cultural preparation who have forgotten and removed common knowledge along with the traditions and behaviors that it built as well as the limits of precaution that were given or respected. Examples are numerous and, in terms of my particular field, concern especially the knowledge that was cumulatively built during the course of an ancient and memorable relationship with territory, with the potentialities and the risks connected to its use, with the art of building and producing and with its different declinations according to different climatic conditions and the relative abundance or shortage of specific materials and resources. Studies have been conducted by experts in Italy such as E.Benvenuto, A. Giuffrè, S. Di Pasquale and P. Marconi or, in different fields, P.Bevilacqua or G. Beccattini; they have shown the sophistication, for example, of the constructive and hydraulic tradition and the specific hands-on "how to" knowledge present in certain districts and regions. Often this sophistication was too casually ignored by the encoded bodies of knowledge, by the most recently formulated techniques, by the progressive engineering of territory, economy and society. We are often amazed at the rapidity with which the technical knowledge accumulated over the long centuries dominated by the awareness of the insufficiency of means in relation to objectives was wiped out by the rapid release of entire populations from the material and technical indigence of rural society; at how this nullification was stimulated by expert knowledge. Often with catastrophic consequences. In recent years, tradition has become a mask, often an invention, that aetheticizes and buries even more critical and embarrassing issues in the history of knowledge and technique.
The meetings to which I refer are more frequently attended by a numerous and variegated series of experts in specific and narrow fields. Rather than bearers of specific knowledge, they often appear (and obviously not always) as bearers of one specific image that they proffer as a kind of influential metaphysics using the frequent aid of elementary graphics, funny idiolects and with a fundamentally didactic attitude. A series of statements build protective zones regarding other actors who act along the lines of totally analogous professional strategies. The specificity of the field for which they declare expertise becomes a strong point for them because it leads to the assumption that narrow specialization corresponds to depth, something that is not always true. Those who carefully observe their arguments and language quickly realize that what is proposed on these occasions, even the most formal ones, is more imagery than knowledge - imagery which is sometimes the setting for real elements of innovation.

The opposition of the imaginary with knowledge does not certainly date from today. And it is imperfect because every body of knowledge contains, in its most secluded folds, an imaginary of which it is not often aware. And every image often refers, in partial and distorted ways, to knowledge that has often been forgotten or removed. Contemporary society seems to move, at least in my field, more in terms of the imaginary than in terms of knowledge.
Some images are nothing less than the projection of an individual or group interest upon an entire society; in others it is possible to recognize the extreme expression of a trend underway; others still are images of contrast, created in diametrical opposition to other images; others finally, perhaps more rooted, but also more hidden, are images gradually created out of collective experience. I have always been surprised by the adhesion of these images to the fundamental nucleus of modern urbanism's program: I repeat - to its program, even if not always to its forms.
I don't imply image, or the imaginary, as the representation of dreams or desires but as a construct of the imagination. To explain what he means by this term, H. Putnam resorts to the story of a mountain climber who is partly stuck. With a partial, and perhaps distorted, vision of the wall, and with the means and the partial knowledge at his/her disposition at the moment of difficulty, the climber "imagines" a route, appraises its risks and possibilities for success and discards it while "imagining" a second or third or nth route whose risks and possibilities appear even more convincing. We will only know if the climber is saved and not whether the evaluations that led him or her to reject some of the possible routes were correct; we won't even know, in the case of success, if the chosen route was the best one among the possible choices. In general, the history of mountaineering tells us that it was only one of many possible routes.
Today, the urbanist - and the city - are in an analogous, and likewise risky, situation. Bewildered by many voices recommending the imagined route, they know that all voices must be heard, but that the route cannot be constructed according to the surface value of the discourses of the different participants in the meetings, that it cannot be the mere result of a process of negotiation among attendees.
The idea of a collective project for the city, always using the terms in their broadest sense, while knowledge relating to specific histories of cities progressively accumulates, appears ever more as a great rhetorical figure - something on the edge, an unattainable point of escape. This renders the reflexive urbanist, if I may, a tragic figure. Compelled, from the observation of the partiality of many disciplines, to have an elitist conception of his/her role (in the meaning given to the term by Mosca, Gramsci and Bourdieu) - one often interpreted in terms of the avant-garde - but aware of the related risks of its decline into an unbearable and moralistic arrogance, the urbanist, perhaps more than others, but not totally alone, has the penchant to reflect upon the role, that, in the words of E. Morin, a "well-trained mind " should occupy in contemporary society; it is a kind of knowledge practice that does not seek its reputation in the progressive narrowing of its own field of investigation and in specialization, but in the ability to build connections and interactions through time, space and the knowledge that has crossed them; trying to imagine situations that are better than the original ones along with the ways to attain them.
Imagination has played an important role in the history of modern science. This is the reason why Putnam calls it to our attention, blurring the boundaries between science and artistic practices. Besides the contingency of negotiation, imagination is what can be brought to the project for the city.

The histories of urbanism, greatly indebted to the histories of architecture and art and the disciplinary divisions within the different academies, are all written as critical recountings of plans, projects and policy, and of their successes or failures. Few have been written as the histories of a specific professional group. A history of western urbanism has not yet been written, at least in reference to planning during the last hundred and fifty years, as the story of intellectuals who attempt to recapture a line of thought constantly dispersing within the myriad branches of specialization or local knowledge, and which, time and time again, opposing their paratactical combination, attempts to make different constellations of knowledge and practices interact and interbreed. And often by doing this, paying a steep price in terms of the reputation in the scientific community, anticipating, or at least intuiting, themes that will become the substance of specific research projects and knowledge practices in following years. Yet to me it seems that it is only in the eventual proof of the positivity of this attitude, rather than within the enclosure of one's own discipline, that urbanism's prestige can be reconstructed.