RATIONALISM. – A relatively recent philosophical term (it entered into use with English deism [v.] in the 17th century) and rich in meanings. Three fundamental senses may be distinguished: 1) metaphysical sense; 2) epistemological sense; 3) religious sense.
I. Metaphysical sense
Everything has a reason for being, and there is nothing, at least in principle, that is not rational. Reason [v.] is, in short, the first principle of universal intelligibility, and everything that exists, in itself even if not for us, is reducible to the essential laws of rational thought, understood as the principle of reason of things, even if the inadequacy of our cognitive means cannot fully grasp this profound rationality of the universe in its unity and totality. In this sense, rationalism may be pantheist, theist, or, if the term is permitted, semi-pantheist: pantheist if it identifies the rationality immanent in the world with God Himself (Stoicism, Plotinus, Spinoza, Hegel, etc.); theist if it derives it from the creative act of God, who is transcendent with respect to the world (Plato, St. Augustine, St. Thomas, Vico, etc.); semi-pantheist does not identify God with the principle of reason immanent in the world, but makes of the world itself, in its “universal harmony,” the “best of all possible worlds,” which God could not fail to create by moral necessity (Leibniz). In all these cases, however, it is admitted that: a) the world has an order and a purpose, and nothing in it is left to chance; b) if it seems otherwise to us, this is due to the imperfection of our knowledge and to our limitations as finite and contingent beings, who are unable to perceive the great economy of the universe, whether it be due to the immanent Reason that governs it (pantheist thesis) or to Providence that realizes a mysterious divine plan (theist thesis).2. Epistemological sense
The sole source of knowledge of truth is reason, the essential and exclusive faculty for this purpose. In this sense, rationalism opposes all forms of sensism [v.] and empiricism [v.], which take as sources of truth (and of every truth) the associations, classifications, and schematizations that the intellect makes of sensible data. From this point of view, one may speak of a rationalism of Socrates [v.] and Plato [v.], which opposes the sensism of the Sophists [v.]; of Descartes and Leibniz [v.], which opposes the empiricism of Locke [v.], etc. Naturally, not all forms of epistemological rationalism exhibit the same rigidity and exclusivism. In antiquity, the rationalism of the eclectic school, and above all that of Parmenides, had this character, considering all sensible experience as illusory and deceptive: Justice, who “holds the keys that open and close” (i.e., reason), welcoming the philosopher, declares two things to him: that there is the field of science, which is the “well-rounded truth,” and the field of opinion, which is unworthy of belief, i.e., being, which is intelligible and of which there is truth, and not becoming (the sensible), which is appearance and of which there is only opinion (Sextus Emp., Adv. math., VII, 111 ff.). One must judge not with the eye that does not see and with the ear that echoes illusions, but with reason (ibid., VII, 114), the only faculty that affirms the unity of being. Socrates and Plato mitigate the intransigence (and abstractness) of Eleatic rationalism, and both do not deny the importance of the senses, excluding sensation from the cognitive process. With Plato, however, rationalism assumes the essential character of being “innate,” which, with various nuances or deepenings, will be preserved by the entire Platonic tradition: in the human soul there exist knowledge-principles or rational forms, etc., prior to any external experience, which reflection [v.] discovers. Sensation is merely “the occasion for awakening in the soul the innate knowledge that has been forgotten” (see especially the Meno). This allows Plato to neither exclude nor devalue the intermediate stages of knowledge (see especially the Theaetetus), but it does not permit him to grasp the true value of the sensible and of feeling. For him, true knowledge is that of intellection (νόησις) and discursive thought (διάνοια), which is directed toward the Ideas, the entities that remain always identical to themselves and which can only be grasped by thought (Phaed., 79 a), the only faculty that enables us to acquire truth and wisdom (ibid., 66 a; Resp., 508 d). Aristotle [v.] removed the Platonic inanimate and vindicated the value of sensible knowledge as the origin of all our knowledge, always leaving primacy to rational truth. Of all things we have certainty either by syllogism or by induction. We learn either by induction or by demonstration. Demonstration proceeds from universals, induction from particulars (Analyt. pr., II, 23, 68 b 13). These two classical forms of rationalism are found in Christian Platonism (St. Augustine, St. Bonaventure) and in Christian Aristotelianism (St. Thomas), deepened, the former in the sense of the “interiority” of truth (distinct from the inanimate) and the latter, which contains strong Platonic-Augustinian elements, in the sense that, in addition to ratio, it admits (as indeed Augustine does) intellectus, a higher and intuitive faculty of knowing, although the two are not two different powers: “Etsi intellectus et ratio non sunt diversae potentiae, tamen denominantur ex diversis actibus. Intellectus enim nomen sumitur ab intima penetratione veritatis, nomen autem rationis ab inquisitione et discursu” (Sum. Theol., 2a-2ae, q. 49, a. 5 ad 3).But the term rationalism has acquired a precise philosophical meaning, which is the one now in use, only with Descartes (v.) to Wolff (v.): within us there exist a priori principles (innate, albeit in a “virtual” state) that are self-evident, of which every true knowledge is a necessary consequence, to which the senses add nothing. It should be noted that modern rationalism develops contemporaneously with the formation of modern science: rationalism and scientism are inseparable. Hence the demand for a purely rational truth, capable of dominating and ordering the confused material of sensible experience. Yet both rationalism and empiricism (v.), which opposes it, lack a critical concept of experience itself and confuse it with the “empirical datum”; thus rationalism lapses into an apriorism of forms without content, while empiricism lapses into a mass of sensible data without any rational form valid for the discovery and attainment of truth.
Rationalism also signifies the rational dominion over reality and the autonomy of reason itself from every other authority: if reason is innate to man and within it are innate the principles of every truth, it is independent of tradition, grounded in itself, rejects all that is not reducible to it, “critiques” every other authority, and constructs its own “natural” law, its “natural” morality (no longer of divine origin, either one), and its “natural” religion (without dogmas and without Revelation). For rationalism, it suffices that reason be free to realize itself fully for total truth and a wholly rational knowledge, entirely complete and absolutely perfect, to be achieved. Thus rationalism presents itself as a revolt against tradition (even religious) and history, from its founder R. Descartes, whose Discourse on Method is its manifesto (v. especially part 2).
From the epistemological standpoint, the position of rationalism seems well defined by Leibniz: “The knowledge of necessary and eternal truths is what distinguishes us from mere animals and gives us reason and the sciences, elevating us to the knowledge of ourselves and of God” (Monadology, no. 29), without any role for sensible experience: “Pure and naked reason, distinct from experience, has to do only with truths independent of the senses” (Theodicy, Discourse on Conformity, 1). Thus rationalism, linked to science (v.) and its development, dogmatically assumes as the typical truth of knowledge that of physics and mathematics: the rational construction of the world, deduced a priori through analysis and culminating in a Cause or a Law, identified with God, who guarantees the perfect functioning of that “machine” which is the cosmos.
Therefore, “the critical position of rationalism is not one of critique of reason, but of whatever is not reducible to rational knowledge: the absoluteness of reason, dogmatically assumed, is critically employed as the measure by which everything must be measured... For rationalism, everything is rationally clear, and what is obscure is an inferior degree of knowledge; all problems are well defined and resolved: reason adapts the natural order, and the natural order belongs to a reason of reason. In a world without philosophical enigmas, there is no longer any need for religious mysteries, the fruit of fanaticism and superstition, as concludes the barbaric scientism and superficial philosophism of the Enlightenment (v.)” (M. F. Sciacca, L’interiorità oggettiva, Milano 1952, pp. 53–54).
It is precisely this “reason” of rationalism that thoroughly critiques empiricism, opposing the view that all human knowledge derives from sensible experience, which is the insurmountable limit of reason. Into this Kant (v.), in which rationalism acquires a new meaning in relation to the new significance Kant gives to the term “experience” (v.). Experience is not the empirical datum: this is merely the content of experience, which is possible because the mind possesses reason, that is, a system of a priori forms that organize and systematize the empirical data. Therefore, experience is the synthesis of the a priori form and the a posteriori empirical datum, which finds its order in the form and gives its content to the form.
Consequently:
a) the a priori principles of rationalism from Descartes to Wolff cease to be innate truths and become, with Kant, “conditions” a priori that the intellect applies to empirical or sensible data so as to elevate sensory knowledge to the level of rational knowledge and to construct that synthesis which is experience;
b) “knowledge through reason” (Vernunfterkenntnis) and a priori knowledge are “the same thing” (einerei), inasmuch as it is reason that contains the principles that yield a priori knowledge (Critique of Pure Reason, Introduction, § 7);
c) but since the principles are transcendental conditions or forms a priori, their validity remains limited to empirical or phenomenal experience;
d) and thus Kant, like empiricism, takes the sensible as the limit of reason and can no longer avoid metaphysical agnosticism.
In this way, with Kantian criticism, rationalism comes to be identified with the possibility of physics and mathematics as sciences, without, however, managing to avoid the subjectivity of knowledge, given that the a priori is not a truth but merely a condition (the transcendental activity of the subject) of experience.
After Kant, but through the development of Kant, Hegel (v.) makes Reason the metaphysical principle, identifying the “real” and the “rational.” For Hegel too, the Idea is transcendental, but no longer a function or condition of experience; rather, it is a metaphysical entity that, through Hegel, is reality itself and resolves within itself all that is real, not only the phenomenal, without any remainder of the thing-in-itself. Thus metaphysical agnosticism (v.) is eliminated—not because Hegel (and all transcendental idealism) found and resolve the problems of metaphysics, but because they dissolve metaphysics into logic, that is, being into thought. Therefore, in Hegel, metaphysical and epistemological rationalism are identified, and dialecticism (the passage from one term to the other of contradiction and the unity of contradictories; Encyclopedia, § 81) is at once the law of thought and of the real. Thus rationalism once again dogmatizes itself and, in positing itself as total truth, denies its own truth and every truth in the “irrationality” of its absoluteness and in the “abstractness” of its panlogism.
### Religious Sense
It would be more accurate to say "irreligious," since the so-called "natural" or "rational" religion resolves itself into the negation of religion, inasmuch as it reduces all its content of truth within the limits of reason. Therefore, rational religion is that doctrine or doctrinal attitude which admits of religion only those truths that can be known rationally. Strictly speaking, one cannot speak of a rational religion before Christianity, since there was lacking a revealed truth, and hence a truth that is suprarational and dogmatic. Rational religion begins with English deism, according to which religious truths are accepted not because they are revealed, but insofar as they are comprehended and justified by reason. Thus, the truths of faith are denied, and religion is made a degree of reason itself or is dialectically resolved into philosophy (Hegel, Gentile), of which it is an inferior degree. A doctrine heterodox in every respect (naturally condemned), inasmuch as it denies Revelation and subordinates religion to reason; in fact and in law it denies it, inasmuch as it denies dogma and the supernatural. To combat rational religion, one must not fall into the "opposite excess" (also heterodox) of the "irrationality" of revealed truth (as if it were "absurd" to reason: Kierkegaard, Barth, etc.) or into fideism (q.v.), which, by denying reason, loses faith itself. To rational religion, religious "irrationalism" is not to be opposed, since revealed truth is not against reason, but above it without contradicting or opposing II. Indeed, it can be defended negatively by reason (by demonstrating the falsity of the contrary assertion), while remaining a suprarational and dogmatic truth. See also, for the theological aspects of rational religion, GRACE; MYSTERY; REVELATION; SUPERNATURAL.
### Rationalism
Kant, Gentile, Hegel, D. D. D.