SENSISM. – A philosophical system or trend that admits sensation (v.) as the sole source of knowledge and resolves all forms of thought (v.) into II. Sensism thus opposes any substantial distinction between sense and intellect, between perception and concept (v.). It is distinguished from sensationalism, which understands reality itself, in a phenomenalistic sense, as a sensation, and from sensualism, which in Italian has an exclusively ethical meaning and denotes, in the same sense as hedonism (v.), the system that places the norm of morality in sensible pleasure. Terminology is elsewhere more uncertain: in French, German, and English, “sensualism” is in fact used with the meaning of sensism, a term lacking in these languages (recently, W. Brugger has introduced [Sensismus] in his Philosophisches Wörterbuch, Vienna 1948).
Sensism represents, in a certain sense, the antithesis of rationalism (v.); deriving all knowledge from experience, it opposes the various forms of innatism (v.) and logically entails the negation of any theoretical knowledge valid beyond experience itself (positivism [v.]).
The first formulations of sensism, though with a meaning intended to be merely psychological, appear in pre-Socratic philosophy. Indeed, despite the epistemological dualism that emphasized the distinction between opinion or vulgar empirical knowledge (δόξα) and truth or rational knowledge (ἀλήθεια), in Parmenides there is an affirmation of the substantial identity between thought and corporeality (Diels, fr. 16 B, I, p. 244, 8; Aristotle, Met., III, 5, 1009 b 21–25; fr. Gli eleati, ed. P. Albertelli, Bari 1939, p. 155). For Empedocles, “to think and to perceive are the same thing” (Aristotle, De anima, III, 3, 427 a 19–20; cf. Met., III, 5, 1009 b 12–13), and according to Protagoras, “the soul is nothing apart from sense” (Diogenes Laertius, IX, 51; cf. Plato, Theaet., 152 a, c): this sensism of Protagoras, which was posited as a premise of epistemological relativism, insofar as sensible perception, conditioned by the individual subjective-objective moment, lacks universal validity. Stoic epistemology is also sensistic: “Through the senses, nature offers us the notions of things” (fr. 66: N. Testa, I frammenti degli stoici antichi, I, Bari 1932, p. 36; cf. fr. 62, ibid., p. 32): experience, concepts, and science have sensation as their sole source. Epicurus’ school is equally explicit in its sensism: “All rational knowledge arises from the sensations” (πᾶς λόγος ἀπὸ τῶν αἰσθήσεων ᾖρτηται: Diogenes Laertius, X, 32). In early Christian thought, Tertullian inclines toward sensism, as does Arnobius, not without Epicurean influence (cf. Adversus Gentes, II, 16–20 sqq.: PL 5, 833 sqq.). Medieval thought, even in the nominalist trend of the 11th and 14th centuries, maintained the substantial distinction between sense and intellect, and thus sensism cannot be attributed to scholasticism: the principles of sensism, however, were latent in the devaluation of universal knowledge by Occam (v. Nominalism; Occam). It is equally CAMPANELLO (v.): he holds that the universal, as idea and concept, if not as common notion, transcends sense: “homini... mentem divinam immitti, quandoquidem in eo apparent operationes quae non in caeteris” (Prodromus, Frankfurt 1617, p. 85, in G. Di Napoli, T. Campanella, Padua 1947, pp. 278 sqq.).
In modern thought, HOBBES, THOMAS (v.): there is no distinction between soul and body, and thus “all knowledge arises from sensation” (cf. Leviathan, I, 1 and 34), understood passively as the motion of the organic subject toward the object; deterministic-mechanical association accounts for all psychic processes. LOCKE, JOHN (v.), although he affirms that every idea comes from experience (Essay, II, 1, § 2), nevertheless goes beyond sensism, inasmuch as he recognizes, alongside sensation, reflection or internal perception—the soul’s perception of its own acts—as a source of knowledge (ibid., 4 sqq.). Sensism is associated with materialism (v.) in La Mettrie: the entire psychic life is a function of the brain, and every content of knowledge derives from the senses and resolves into sensations. In La Mettrie, Helvétius (v.), sensitive materialism translates, on the ethical plane, into hedonism: there is no other moral criterion than utility and individual interest, even if pursued through obedience to laws; to be “moral” is ultimately a way of being happy. The most typical expression of sensism is found in French Enlightenment thought in Condillac (v.). He accepts Locke’s empiricism but resolves into sensation even the second source of knowledge, reflection: “sensation unfolds all its faculties” (Traité des sensations, I, 7, § 2). All contents of knowledge and all its functions are therefore nothing but sensations elaborated and transformed (“sensations transformées”): attention, abstraction, reflection, analysis, synthesis, imagination, comparison, judgment, syllogism are merely characteristics (vivacity, persistence...) or relations (of concomitance, succession, coordination, similarity, distinction...) of sensations. Similarly, in the affective sphere, all feelings (love, fear, hope, desire, will to good...) derive from the fundamental character of pleasure and displeasure inherent in sensations. But, unlike La Mettrie (whose materialism, as Lang has shown in Geschichte des Materialismus, I, part 1, ch. 2; Italian trans., Milan 1932, pp. 337 sqq., does not derive from Condillac’s sensism), Condillac preserves a spiritualistic tone in his sensism: he does not exclude the existence of a spiritual soul, distinct from matter and motion, as the subject of sensations (cf. De l’art de raisonner, I, 3). Condillac’s sensism, as a systematic empiricism of the genesis and development of knowledge, enjoyed great success and became, in France, the official philosophy of the second half of the 18th century (v. IDEOLOGY); among the “ideologues,” Ch. Bonnet (v.) preserves a spiritualistic character in sensism. It was imitated in Italy by Romagnosi (v.), Soave (v.), Borrelli (v.).
In itself, sensism is linked to the developments of materialism: Robinet; Cabanis (there is no soul distinct from the body; psychic functions resolve into chemical nervous processes [Diderot had understood them as mechanical processes]); thought as a secretion of the brain; Czolbe (consciousness is a pure copy of material reality, and even its representations possess extension, cf. Neue Darstellung des Sensualismus, Leipzig 1856); Feuerbach (formal: morality and action are directed solely by the search for happiness, of which sensation is the criterion). Sensism is also associated with Humean empiricism (v. HUME): “the power of the mind and of thought is ultimately nothing but the faculty of compounding, transposing, augmenting, or diminishing the materials given by the senses and experience” (Enquiries, sect. II, § 13, ed. Selby-Bigge, reprint, Oxford 1952, p. 19); nor is it foreign to the postulates and motifs of positivism and neopositivism (v.). In France, it was opposed by the spiritualist trend of Maine de Biran, Jouffroy, and Cousin.
The saint presents a positive instance already asserted by Aristotle against the innatist idealism of Plato and accepted by Thomism: the objective-functional dependence of the activity of thought upon the forms of sensibility. The principle “nihil est in intellectu quod prius non fuerit in sensu” (cf. St. Thomas, De verit., q. 2, a. 3 ad 19) may have a correct meaning, inasmuch as no object is made actual in thought without an immediate or mediate relation to the data of sensible knowledge: “sine sensu non potest aliquis homo addiscere, quasi de novo acquirere scientiam, neque intelligere, quasi utens scientia habita” (St. Thomas, In De an., III, lect. 13ª, ed. Pirotta, n. 791). But this does not mean that the function of the intelligence is exhausted in sense. The concept (v.) rather presents itself as interpretation and emergence, on the plane of being and its absolute principles, of the empirical content of sensation. The intellect therefore manifests an essential noetic transcendence, as disclosed by the significance and universal values of experience. Sensible knowledge is not therefore adequate as the principle of conceptual elaborations: it is not, as St. Thomas expresses it, “totalis et perfecta causa intellectionis, sed magis quodammodo est materia causae” (Sum. Theol., 1ª, q. 74, a. 6, c., in fine). Equally irreducible to sense is the knowledge which thought has of itself as self-consciousness (v.) and reflection (v.).
The saint involves, in its developments and systematic exigencies, on both the theoretical and practical planes, relativism (v.).