141 There are terms that, instead of framing a precise definition, tend to absorb meanings. Sustainability is certainly one of these. Those who pronounce it can understand extremely different things, and even greater is the variety of interpretations possible for those who listen to this word, inevitably projecting their beliefs and expectations on it. As architects, we make far too wide use of it: forced by the urgency of the issues involved and, at the same time, inclined to exploit the intrinsic "goodness" of the concept (who could claim to be against a responsible use of resources?), we often end up being victims of the ambiguity of its operational applications. A particularly thorny and cumbersome aspect lies in the ethical overload of eco-bio-social-sustainable approaches . The persuasive effectiveness of their arguments replaces any other consideration, inside and outside the discipline, confining on their specific terrain the critical assessments that aspire to some relevance. The Vertical Forest ( Stefano Boeri Architetti , Milan, 2007-2014), for example, is a brilliant project and communication operation that owes its name, and its success, to the "condominium green" spread on the elevations. It is a controversial solution. Planting trees on cantilevered terraces is not exactly "natural" and bringing them upwards involves a complicated maintenance management. It also involves an increase in loads on the structure and, consequently, a greater use of materials, such as to affect the overall energy balance and that related to emissions. Among the commentaries about the work there are those which, indeed, question the positive impact of the building in social and ecological terms and those which, on the other hand, highlight the ability to concentrate, and bring to the city, a vast equivalent natural surface. However, quantitative issues prevail, so much so that almost no one, even among architects, has considered more visual aspects. Still, the figure/background relationship between plants and elevations is carefully managed and takes advantage of the black/white contrast of the coating surfaces, as of the abstract geometry of the backgrounds. The resulting vegetal overexposure effect is a decisive factor, capable of representing the local benefits on microclimate and air quality, way beyond their actual occurrence: an effect asking to be masterfully designed, so that the narration of the project could be accelerated by its image. However, this is a form of subliminal communication, using the "disappearance" of architecture as a means to sanction its effectiveness in the role of "sustainable" project. After all, that a building somehow symbol of the Anthropocene era tends to hide the artifice that makes it possible does not lack its own logic. An eco-cosmetic approach may also turn out to be more coherent, and even paradoxically sincere towards itself and the others, compared to project researches declaring and pursuing any performance efficiency target in terms of energy, as in a social and ecological way. The rhetoric supporting them, both derived from and in opposition to the modernist vision, revisits in a sustainable key the direct relationship between function and form well proposed over a century ago by Louis Sullivan. The "eco-efficient" project seems to re-propose the same positivist confidence, trusting in the ability of ideological penetration with regard to functionalist simplifications, but exposing itself to even greater risks of failure. As is widely known, the attempt of the protagonists of the Modern Movement to transfer into the organization of space the linear logic of Taylorist production – the rigid division of tasks and times within the assembly line – came up against the difficulty of maintaining a vertical control over complex systems and their growing indeterminacy. The sustainable hypothesis, holistic by definition, obviously involves much higher levels of complexity than functionalist logic, and therefore requires an even more pervasive surveillance of individual behaviours and their collective integration, with an exponential growth of problems as the scale increases. Masdar , the city designed by Foster+Partners in 2006 near Abu Dhabi airport with the aim of neutrality in the carbon cycle, represents a significant experiment from this point of view, also for the contradictions that it contributed to highlight. Conceived for fifty thousand inhabitants and only partially built, Masdar faced the financial crisis of 2008 by radically downsizing its objectives and, above all, by reviewing the basic strategy intended to carry them out. The latter was essentially based on a systematic isolation between internal and external, not only from the construction point of view, but also from the urban, social and mobility ones. Inscribed in a square and equipped with self-driving electric shuttles, Masdar was to function as a gated community, a walled city capable of controlling the incoming and outgoing flows of materials and, above all, of people. These were divided between residents, whose programmed number could obviously not vary, and commuters not allowed to stay inside the fence (generally, foreigners with limited rights according to the so-called Kafala "sponsorship" system for immigrant workers). In other words, the urban machine was considered virtually non-modifiable and its energy neutrality would have nevertheless produced a considerable mass of " wasted lives ".