Rationalism (from the Latin word ratio, “reason”) is a philosophical movement based on the assumption that human reason can in principle be the source of all knowledge. In other words: philosophical movement whose foundation is the persuasion that reality and being are structured in the same way as our thought and that therefore the relationships that regulate the rational process are equal to those present in the organization of the external world; hence the belief that reason has the ability to penetrate into external reality and to exhaust its knowledge.

In general, rationalist philosophers argue that, starting from “fundamental principles”, identifiable intuitively or experimentally, such as the axioms of geometry, the principles of mechanics and physics, you can get through a deductive process to any other form of knowledge.

Rationalism was formed from different philosophical orientations, which occurred in ancient Greece, the Middle Ages, the Renaissance and the modern age. In general are defined rationalists those philosophical systems in which reality is seen as governed by a series of laws and principles that are perfectly understandable with human reason and coincide with the thought itself.

It is in opposition to irrationalism, which instead favors other human intellectual faculties related to instinct, blind will, skepticism, etc. In modern thought, starting with Descartes, rationalism will be opposed to empiricism, when the discriminating element will not be reason, but the relationship between reason and experience. Rationalism is also a pedagogical orientation that has confidence in the possibility of increasing human knowledge by the individual and society, as mediated by knowledge.

Platonic thought

The first coincidence between the “copulative” meaning (union of a subject to its predicate) of being and the “existential” meaning is found in Parmenides: there is identity between the logical being that unites a subject to its predicate and the being that affirms the existence of an object, therefore an object thought as rational is automatically also real. A difficulty arises, however; what is the origin of the terms that reason uses in its logical relations? If they derive from the senses, their perfect correspondence with reason would presuppose a superior ordering mind that has preordained both the senses and reason, and therefore the order of the world would be identical to the rational one even before this identity is proven; if, on the other hand, the terms used by reason are already in itself at the moment it sets out to know the external world, from whence has it drawn them? Plato derives them from the perfect intelligibility of “infinite being”.

But the infinite being is the object of an intellectual intuition, not of a rational demonstration and therefore it is indifferently rational and irrational. And on the other hand, the infinite being, when it wants to define itself, breaks up in the multiplicity of finite beings and these do not have as their own prerogative the perfect intelligibility, which instead is only of the infinite being. Plato tries to overcome this difficulty by exalting love, which would allow to bypass the finite beings and reach the infinite being, in which there is the vision of the rational world. It is therefore the philosopher himself to suggest two forms of rationalism: one that wants to establish a relationship between the data of the senses, remaining in a contingent order; the other that instead claims to draw an absolute logical order, which has in itself its universal terms, an order that is eternal and absolute. But in this case it remains to be proved how such an order can coexist with the sensible world. In reality it is a transcendent world, the prerogative of neo-Platonic mystics and of similar trends that have renounced rationality as knowledge of external reality.

Modern thought

In modern times rationalism will become dogmatic: between sensible world and rational world (innate to human mind) there is a dualism that is resolved only in God, guarantor of the relationship between the two worlds. In Spinoza the rational order has the task to free from passions; in Leibniz the sensible world is only an entity in power; in Kant reason does not create the world of concepts, it is no longer a logical law, but it becomes a value, a moral act, the duty that gives cohesion to the whole content of consciousness: a rationalism, therefore, only in a broad sense because the world of sensible objects remains heteronomous and cannot be dominated by reason.

Trust in reason is the fundamental leitmotif of the Enlightenment, the true force that not only eradicates all obscurantism, but attacks reality and transforms it: the flat and simple logic of the rational overwhelms and destroys the fetishes of irrationality, ignorance, prejudice, superstition, fanaticism, intolerance, despotic authoritarianism, inert tradition and makes the meridian light of the intellect shine in all minds, redeeming them from every constraint to bring them to the freedom of homo novus, homo rationalis.

It is useless to ask Enlightenment rationalism for a precise physiognomy, like that of Spinoza or Kant’s; it is anti-dogmatic and anti-metaphysical, it is experimental and scientific, but only for problems that adhere to man and are immediately practical, it has the capacity for abstraction, but pursues only those formulas that have in themselves the capacity to renew reality, it is above all optimism in man’s reason and in the educative virtue of science. A synthesis of reason and action, the Enlightenment puts a renewed will next to enlightened reason, cuts all bridges with the past and pushes them towards the new lands of the future.

Trust in reason has again its exaltation in idealism and receives its consecration from the Hegelian identity: “all that is real is rational; all that is rational is real”. That is, we return to classical rationalism, in which rationality is also expressed as existence. Hegel believed in this way to have overcome the obstacle of the sensible world, affirming that this does not exist independently from reason, but only as part of the rational order; in reality, the difficulty of rationalism was only revealed in a more macroscopic way: in an order in which the law is already all known, there is no more place for the freedom and creativity of conscience; the Kantian conquests of thought as the work of conscience and reason as moral duty are thus suddenly dispersed.

Rationalism in architecture

The multiform manifestations of rationalism in architecture can be traced back to a new approach to design practice, which refers to the logical processes of science and technology. Rationalist (or rational) architecture was born from the necessity of a more real adherence to the social and economic reality resulting from the industrial revolution, aiming at a rational solution of the problems that this same society, the needs of industrial production, the new dimensions and functions of the city pose to the architect and the urban planner.

In open and conscious polemic with the romanticism and irrationalism of Art Nouveau and with the Academies, rationalist or functionalist architecture (both terms have been used indifferently by the same animators of the movement and by the critics, given the commonality of intentions and the similar results) wanted to be part of history rather than art, creating forms whose determination is entrusted to the analysis of the functions to which the architectural organism or the object of use is intended and the choice of the most appropriate construction techniques or industrial, through the elimination of any emotional and aesthetic component and the “purification” of the form from any decorative apparatus.

The movement, to the formulation of which have contributed the contributions of historical materialism and positivism, as well as the legacy of Arts and Crafts and the solicitations of modern figurative culture, from cubism to neoplasticism, has reached its phase of maximum vitality in the years between the two world wars, on the one hand in the theoretical-didactic work of Walter Gropius at the Bauhaus and in the activity of Mies van der Rohe, on the other in the theoretical (Vers une architecture) and practical work of Le Corbusier, assuming the physiognomy of a current of international importance and decisive for the developments of Western architecture.

In the years between 1920 and 1940, European Rationalism developed its problematic physiognomy in the original work of its greatest architects, from Breuer to Scharoun, from Behrens to Poelzig, and the debate on renewed architecture was polarized around the new urban planning initiative of Weissenhof (Stuttgart), the competitions for the Chicago Tribune (1922), for the headquarters of the League of Nations in Geneva (1927) or for the Palace of the Soviets in Moscow (1931) and, from 1928 to 1940, in the meetings of the CIAM, official organs of European rationalism.

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