SCETTICISMO. – From Greek σκέπτομαι, I look, observe, reflect, meditate, investigate, it is the attitude—and systematic position—that does not admit, in general or with regard to a given order of objects, the possibility of certain and definitive assertions. From antiquity onward it has been opposed to dogmatism ([v.] from δόγμα, δόξα, δοκεῖν, to opine, to pass judgment). S. is therefore the negation of a form of knowledge possessing the significance of absolute truth and permitting a theoretical conception of reality and life.
The essential condition of s. doubt (v.) concerning the value, nature, and meaning of reality and experience, and consequently renunciation (ἐποχή) of every judgment that goes beyond the immediacy of experience itself. This is the so-called total (or universal) s., which must not, however, be understood as the negation of any certainty. Indeed, no form of s. can be conceived that extends doubt to experience itself (v.) as such. Every skeptical attitude finds in experience, as the very reality of the doubting consciousness, its insuperable limits and therefore permits, within the sphere of phenomena, a degree—however theoretically slight—of certainty. Alongside total s., partial expressions may exist—and have existed historically. Thus one speaks of religious, ethical, aesthetic, pedagogical, scientific, etc., s. when, in these individual orders of objects and values, human thought is not acknowledged as possessing the possibility of objective knowledge. Partial forms of s. do not necessarily coexist;
indeed, at times they conflict with one another: religious s., for example, may coexist with rationalistic or scientific dogmatism, while, conversely, s. concerning the possibilities of reason may be associated with extreme forms of religious dogmatism.
The difference between s. as a purely psychological attitude and s. as a systematic position must also be clarified. In the first case, s. is a simple mental disposition, a factual doubt more or less conscious of its reasons; it may possess a greater or lesser degree of seriousness (s. “frivolous,” “fickle”), according to the differing spiritual value and moral sincerity of the person who professes II. As a systematic position, s. presents itself instead, in its own way, as a (negative) philosophical conception derived from factual and principial premises; it may assume the form of “dogmatic” s. if it is expressed in the formula: “certain theoretical knowledge is impossible”; or that of simple agnostic negativism if it is reduced to the following assertion: “one can neither affirm nor deny; the truth-value and certainty of knowledge are doubtful.” Although dogmatic s. displays a character of more absolute radicality, there is nevertheless an essential equivalence between the two positions, insofar as doubt—decisive and definitive—concerning the possibilities of certainty entails its negation. Any position that accepts doubt as a non-decisive but methodical moment, or that is, in any event, an attitude of inquiry that does not systematically exclude the possibility of objective certainty, must instead be distinguished from s. (v. PROBLEMATICISMO). Empiricism and phenomenalism (v.) are analogous expressions of s.: every consistent empiricism cannot fail to agnosticism (v.), which is precisely the essence of s.
The causes of the skeptical attitude have historically been diverse. The principal ones should be identified as follows: the contradictions of thought and existence; the obscurity of problems, reasons, and purposes of things; the uncertainty of values in life and history.
S. received a mature elaboration in Greek philosophy. Partial motives for it can already be found in the Eleatic school (v. ELEATISMO), which regarded the world of the senses as appearance and illusion. A fragment of Xenophanes states: “opinion [as opposed to truth] reigns everywhere,” δόλος δ'ἐπὶ πᾶσι τένταται (G. A. Mullach, I, Paris 1860, p. 103, fr. 14). Sophistry was undoubtedly inclined toward s.: such were Gorgias’s assertions concerning the unknowability of being and the impossibility of a genuinely communicative discourse (cf. Pseudo-Aristotle, De Xenophane, Zenone et Gorgia, chap. 5), and Protagoras’s saying that contrary arguments can be given for everything (Diogenes Laërtius, IX, 51), an anticipation of the ἰσπέδεια τῶν λόγων of the skeptics. The skeptical school also appealed, in addition to Heraclitus, Zeno, Parmenides, Anaxagoras, Empedocles, Democritus, etc. (cf. Diogenes Laërtius, IX, 71–73; Sextus Empiricus, Phyrrh. hypot., I, 220 ff.; Cicero, Acad., I, 72 ff.), to Socrates and Plato. In reality, the certainty Socrates possessed concerning moral science (the profession of ignorance in him was not s., but a methodical moment of knowledge: cf. Apol., 21 b–d) and Plato’s positive dialectic exclude s. At most, latent motives for it can be identified in the unknowability of nature, affirmed by Socrates, and in the meaning of appearance attributed by Plato to the world of the senses.
S. in the proper sense was affirmed with Pyrrho of Elis (ca. 365–370 B.C.; V. PIRRONISMO). According to Brochard, the s. of Pyrrho has a practical character; it does not arise from dialectic but represents a reaction against dialectic; its fundamental idea is: to make doubt an instrument of wisdom and moderation, stability and happiness (op. cit. in bibl., p. 67). It is expressed in the programmatic assertions that later became common among skeptics: nothing is comprehensible (ἐκαταληψία); one must therefore refrain from assent (ἐπαχή); nor can one say of anything that “it is rather so” (ὁὐ μᾶλλον); I define nothing (ὁὐδὲν ὀρῖζω); everything is hidden (πάντα ἀόριστα); nothing is in itself good or evil, just or unjust, and men do everything by law and custom (ὅμω δὲ καὶ ἔθει; cf. Diogenes Laërtius, IX, 61). Hence the various designations of the skeptics: σκεπτικοί, insofar as they are always looking but never finding; ζητητικοί, insofar as they persist in inquiry; ἀπορητικοί, insofar as they doubt; ἐρεκτικοί
(from ἐπέκω), insofar as they suspend every judgment (ibid., IX, 69–70). As a consequence of abstention from judgment, s. posited tranquility or imperturbability of soul (ἀταραξία: ibid., IX, 107); impossibility (ἐπέδεια: ibid., 108) and indifference (ἐπέδεια). The reasons for the skeptical attitude are, in Pyrrhonism, the uncertainty and relativity of perception, and the impossibility of an absolute demonstration, since the validity of demonstration presupposes a criterion, while the criterion in turn requires a demonstration (ibid., 79 ff.). S. is therefore absolute concerning every definition of the nature of things: “The things that we experience as human beings we affirm; that it is day, that we are alive, and many other things that present themselves (παντεύεως) in our life, we know; but concerning those things that the dogmatists claim to comprehend by reason, we suspend assent because we regard them as uncertain and obscure; and we recognize only our affections” (μὸν δὲ τὰ πᾶθη γιγνώσουμεν: ibid., 103); a testimony that supported Richter’s assertion (op. cit. in bibl., I, p. 108 ff.) that Pyrrhonism anticipated Humean skepticism, apart from the subjectivist moment in the English skeptic, absent from ancient s., which calls into question the very existence of reality beyond phenomena. The most illustrious among Pyrrho’s immediate disciples was Timon of Phlius (born in 325 B.C., died in Athens in 235 B.C.), of whose many works only a few scanty fragments remain. Later, Pyrrhonism was taken up again by Aenesidemus of Cnossus (Crete; the date of his birth is uncertain: between 80 B.C. and A.D. 130); and by Agrippa (mentioned in Diogenes Laertius, but of whom nothing is known: Hass holds that he taught toward the end of the first century B.C.). To Aenesidemus (whose Ἰησοῦναι λόγοι, as well as the Περὶ σοφίας and Περὶ ζητήσεως, have been lost) are attributed the ten “places” (τόποι, τρόποι, λόγοι), or reasons for abstaining from assent, transmitted, with slight variations, by Diogenes Laertius and Sextus: perception and representations vary according to: 1) the diversity of animals; 2) the differences found among human beings; 3) the different constitution of the senses; 4) circumstances; 5) situation, distance, and place; 6) the mixtures of objects; 7) their quantity and composition; 8) their relations; 9) their frequency or rarity; 10) institutions, customs, laws, fabulous beliefs, and dogmatic opinions (Sextus, Phyrrh. hyp., I, 36 ff.; Diogenes Laertius, IX, 79 ff.). Five “modes” are likewise recalled from Agrippa: 1) the disagreement among human beings; 2) the proceeding to infinity in demonstration; 3) the variety of objects according to their relations; 4) hypothesis, when, in order to avoid proceeding to infinity in demonstration, a hypothetical principle is assumed as certain; 5) the vicious circle (διέλληλος τρόπος), when as a premise one takes what needs to be proved by the conclusion (Sextus, Phyrrh. hyp., I, 164 ff.; Diogenes Laertius, IX, 88–89).
But even before the restoration of Pyrrhonism by Aenesidemus, s. had been adopted, with Arcesilaus, by the Platonic New Academy (the Ciceronian tradition, followed by Brochard [op. cit. in bibl., p. 29], posited only two Academies, Plato’s ancient one and Arcesilaus’s new one; Sextus [Phyrrh. hyp., I, 220 ff.] gives Carneades’s as the third and reports that others distinguished two further ones afterward). Arcesilaus of Pitane (ca. 315–240 B.C.) was almost contemporary with Pyrrho, but apparently independent of him (Hirzel, Natorp; cf. Credaro, op. cit. in bibl., I, p. 130 ff.): the s. that he introduced into the Academy is essentially dialectical, insofar as it constituted a systematic analysis and critique of Stoic and Epicurean doctrines (ibid., II, pp. 229–30). Against the Stoics’ claim to κατάληψις, “comprehension,” Arcesilaus declared that no perception contains within itself a guarantee of truth: there is no representation that is truly “perceptive,” and opposing arguments prevent assent concerning everything: “Arcesilaus negabat esse quidquam quod sciri posset...; sic omnia latere censebat in occulto; neque esse quidquam quod cerni aut intelligi posset” (Cicero, Acad., I, 45; cf. Diogenes Laertius, IV, 28 ff.). Nevertheless, since in practice a criterion serving as a rule for action is necessary, “he who universally (περί παντός) abstains from judging will conform his acting and not acting to what is reasonable (τῷ εὐλόγῳ; cf. Sextus, Adv. math., VII, 158).” Arcesilaus’s εὐλόγον is therefore (Hirzel, Credaro) purely a practical norm: it is the reasonableness of action in relation to its eudaimonistic end, “prudence, the sense of what is appropriate, the art of living well,” and consequently has no theoretical significance. Arcesilaus’s direction, after his immediate successors, Lacydes of Cyrene, Hegesinus of Pergamum, and Evander, was continued in the Academy by Carneades of Cyrene (ca. 219 (14)–129 (48) B.C.), “homo omnium in dicendo acerimus et copiosissimus” (Cicero, De orat., I, 45). Carneades (he wrote nothing, and his doctrine was transmitted by his disciples) took up in depth the critique of Stoic dogmatism, particularly that of Chrysippus: “If Chrysippus had not existed, neither would I”; Diogenes Laertius, IV, 62). There is no criterion of truth either in reason or in the senses: reasoning, representation, and sensation are sources of illusion and error. Knowledge of things in themselves (πρὸς τὴν φύσιν) is therefore impossible: whether the gods exist or not, whether the world is their work or governed by them, is unknown; the wise person neither affirms nor denies this, but suspends judgment. The same must be said of ethics: moral evaluations are not founded on absolute norms but are pure opinions, varying according to people and times (cf. Cicero, De leg., I, 42). Nevertheless, according to Carneades, there are representations that, in relation to human beings and their nature, seem true and therefore possess probability (εὐθανότης) to varying degrees; this probability is taken as a criterion of practical truth: a plausible representation, contradicted by none of the others and carefully examined, permits the highest degree of persuasion and serves as the criterion for the wise person’s deliberation (cf. Sextus, Adv. math., I, 166–89; Phyrrh. hyp., I, 226–31). Carneades’s πιθανόν (from which his school received the designation “probabilism”) is something more than Arcesilaus’s εὐλόγον, insofar as it concerns the credibility or admissibility of a proposition; but since plausibility is relative to the subject, it does not seem to represent a genuine overcoming of s. (cf. Credaro, op. cit. in bibl., II, p. 68 ff.). Carneades’s teachings were collected by his pupil and successor Clitomachus of Carthage: later, Cicero and Sextus drew upon them (while in the meantime the Academy was returning to Platonism).
Sextus Empiricus ([v.] belonging to the school of the “empiricists”: philosopher-physicians who opposed “art,” observation, experience, and medicine to dialectic) represents, between the second half of the 2nd century A.D. and the beginning of the 3rd (born c. 180), the final expression of Greek s. (he was Greek, although of unknown origin, certainly neither from Athens nor from Alexandria). The writings of his that have come down to us (Outlines of Pyrrhonism, Πυρρόνειοι ὑποτιπόσεις [Italian trans. by O. Tescari, Schizzi pirroniani, Bari 1926]; Against the Mathematicians, Πρὸς μαθηματικούς; Against the Dogmatists, Πρὸς δαγματικούς; the last two works generally brought together under the title Adversus mathematicus) are the most precious source for s. In them Sextus collects, coordinates, and develops, in a systematic, concise, and detailed exposition, all the arguments and doctrines of the ancient skeptics; it is therefore impossible to determine what belongs to him as his own. For Sextus, the essential human significance of s. may be summarized in the following statements: “We do not intend to oppose the common assertions of men nor to remain inactive..., the skeptic does not doubt sensations and phenomena...” (Adv. math., VIII, 157). “Therefore it is sufficient, I think, to live according to experience and without dogmas, in conformity with common observances..., suspending judgment concerning what is stated by the subtlety of dialectic, which stands entirely outside what is useful for life” (Phyrrh. hyp., II, 246; cf. I, 19 ff.).
Christian thought, Revelation (v.), is opposed to s. Partially skeptical motives are nevertheless sometimes found in the undervaluation of rational-philosophical knowledge in the face of faith (cf. Lattanzio, Div. inst., I, 2: PL 6, 117-18; III, 4: ibid., 357-58). S. Agostino had initially inclined toward academic s.: “academicorum more dubitans de omnibus atque inter omnia fluctuans” (Conf., V, 14); later, in the Contra acad. and elsewhere, he brought against s. the certainty entailed by doubt and the truth present within it (cf. Contra acad., III, 9; De Trin., XV, 12; De civ. Dei, XI, 26; De vera relig., 36, 73). Medieval scholasticism, taken as a whole, is alien to s. (apart from the tendency toward theological agnosticism expressed in the so-called “negative theology,” which nevertheless, because of its pronounced mystical character, had an essentially positive significance). The principal source of s., Sextus’s Hypotyposes, was apparently not unknown to scholasticism: a translation of it was in fact discovered in a library of S. Vittore in 1888 by Picavet, and again in 1891 by Baeumker (Eine bisher unbekannte mittelalterl. lateinische Uebersetz, des Hupp. Un. des Sextus Emp., in Arch. f. die Gesch. d. Philos., 4 [1891], pp. 574-77). Skeptical assertions, particularly concerning knowledge of causality in creatures and of the existence of the external world, NICOLA D'AUTRECOURT (v.): in 1347, among other propositions, the following were condemned by Clement VI as his: “Quod de rebus per apparentia naturalia nulla certitudo haberi potest”; “Quod de substantia materiali alia ab anima nostra non habemus certitudinem existentiae”; “Quod nescimus evidenter quod aliqua causa efficiens naturalia sit vel esse possit” (Denz-U, 553-70).
The motives of ancient s. were taken up again in the 16Montaigne (v.): the various solutions offered by philosophical dogmatism to the eternal problems of being, the soul, and God do not permit a reasonable choice; nor can verisimilitude be accepted, since its determination presupposes knowledge of the truth. The grounds of s. lie in the relativity of sensory knowledge, the source of all our knowledge, and in the inevitable circularity of demonstration. It is therefore better, concerning the nature of things and of ourselves, to suspend all judgment and entrust oneself to the guidance of experience and faith, without demanding a rational demonstration from faith (cf. Essais, II, chap. 12; III, chap. 8, 13). P. Charron’s position depends on Montaigne ([v.] Le traité de la sagesse, Bordeaux 1601), reaffirming in the defeat of reason the foundation and necessity of faith. Analogous motives are found in Fr. Sanchez ([1562-1632], Tractatus de multum nobili et prima universali scientia quod nihil scitur, Lione 1581: Sanchez’s position was principally polemical in character, directed against the science of his time). In the 17th century, S. Foucher ([1644-96] Lettres par un académicien, Parigi 1675; Apologie des académiciens, ivi 1687) revived s. Pascal (v.) is known for his statements on the impotence of reason (“la raison impuissante”; “nous sentons une image de la vérité et ne possédons que le mensonge”; Pensées, 434, ed. Brunschvicg, Parigi 1949, p. 229); but their significance lies rather in a confession of man’s insufficiency to realize his existence and spiritual destiny without the help of Grace. Nor is Pascal’s fundamental valuation of human nature in doubt: “je met en fait qu'il n'y a jamais eu de pyrrhonien effectif parfait” (ibid.; cf. also 83, pp. 86-87 and 374, p. 201).
In modern philosophy, the most elaborated expression of s. in the metaphysical sense is Humean phenomenalism (v.). The value of knowledge and reason, which Hume does not intend to reject through the absolute negation of “excessive” s. (Hume does not call himself a skeptic), is nevertheless rigorously confined to the sphere of facts and experience and of abstract quantitative relations (mathematics). Every attempt by reason to go beyond these limits (metaphysics, theology, the search for the cause) is nothing other than “sophistry and illusion” (Enquiries, sect. 12, part 3, ed. Selby-Bigge, no. 132, Oxford 1951, p. 165; cf. the entire section). Hume’s subtle criticism, as is well known, influenced Kant and, through Kant, also later theories of knowledge (against the alleged Kantian overcoming of it, it was reaffirmed by G. E. Schultze [v.] in the Aenesidemus, Helmstedt 1792). S. was not generally taken up again in the negative absolutism of its ancient formulation (which, moreover, had already been systematically brought to completion with Greek s.); but, alongside grandly constructive systems (e.g., idealism), the most radical demands of s. remained operative in recent and contemporary philosophical thought. The task pursued by criticism and by subsequent speculative effort—that of determining the possibilities and limits of reason—has ultimately led, at times through the very same positive solutions, to explicit forms of renunciation of metaphysics (positivism, agnosticism, pragmatism, neopositivism, existentialism). Recently in Italy, a defense of s. was again advanced by G. Rensi (v.): s., as uncertainty regarding every solution to metaphysical problems, is the sole position of intellectual sincerity: “at the moment when [the philosopher] thinks about a metaphysical problem, he cannot fail to perceive, cannot fail inwardly to feel, the opposing solutions as equally possible” (Sic et non, Roma 1911, p. 11).
Against s. there has always been set the internal contradiction of an absolute negation of truth: whoever asserts that he knows nothing knows at least that he does not know, and whoever says that every judgment must be suspended enunciates one: «si nihil sciri potest, necesse est id ipsum sciri, quod nihil sciatur... Sic indictur dogma sibi ipsi repugnans, seque dissolvens» (Lactantius, Dis. inst., III, chap. 6: PL 6, 361). The nature of thought, which is essentially affirmation, does not permit a genuinely universal doubt; thought in act is always, in some sense, certainty: «si dubitat, dubitare se intelligit; si dubitat, certus esse vult; si dubitat, cogitat; si dubitat, scit se nescire; si dubitat, iudicat non se temere consentire oportere» (s. Augustine, De Trinit., X, chap. 10, n. 14: PL 42, 981). This critique of s., while bringing out the intrinsic inconsistency of a negation of certainty that claims to be absolute, nevertheless does not answer the most authentic demands of historical s., which does not contest every certainty, but only that which claims to extend beyond facts and experience. One may agree with Hume «that no one has ever met a person who has no opinion or principle whatever on any subject of a practical or speculative order» (Enquiries, sect. 12, part 1, cited ed., n. 116, p. 148). The consideration demanded by s. («in spite of appearances, Pyrrho, Carneades, Aenesidemus, Agrippa have greatly deserved well of the human spirit»: Brochard, op. cit. in bibl., p. 130) lies elsewhere: in its reminder of the essential dimension of the inadequacy of the human possession of truth. There is no consciousness (whether it opens upon the metaphysical depths of the world, the self, the will, freedom, or action) that does not encounter limitation and opposition, in a content that always refers beyond itself and eludes an absolute, conclusive, exhaustive grasp by thought. This condition, which is the most serious mystery of the human being in search of truth and not assured, in either a theoretical or practical sense, of possessing it, is a limit always present to the possible excesses of philosophical dogmatism. But s. is wrong not to recognize the universality and immutability of the value that becomes present in human consciousness and thought for truth—any truth, even the ordinary truth of life. Hypothesis, probability, doubt, and error certainly accompany, as moments in its development, every effort of thought: the Ἰσσοδεύειν τῶν λόγων is often a reality in knowledge and life. But precisely for this reason, hypothesis, probability, doubt, and error exist and are measured in relation to truth, which, although in its totality it is for the human being only an ideal term, nevertheless structures the mind, thought, and action. The human being is radically in truth through the very fact of thinking, just as he is radically in being, even though both truth and being do not belong to him—as a result of his condition as a creature—as an absolute possession. And the criterion of truth contested by s. is found by the human being in his own intellect, as an expression, however participated and limited, of being and of its fundamental meanings (logical, real, moral), and therefore also as the initial possibility of metaphysics. The very fact that we know how to discern error, discover it, and abandon it confirms that, in general, we possess a norm of certainty. The relative character of sensible knowledge and the variety of human opinions cannot be arguments for s.; they merely confirm that knowledge has a margin of contingency and historicity—
expressed for each person by his particular individual situation in time. The Pyrrhonian demands concerning sensible perception are not difficult to answer through a critique of perception itself that clarifies its subjective modalities and confines its meaning as truth within the terms of an objective but conditioned relation between reality and the subject.
The condition of moral optimism (ἐνταχάξις) that ancient s. posited as a consequence of its negative theoretical attitude is very far from being a necessary derivation from II. A situation of radical uncertainty about the meaning of existence, for a consciousness that searches itself with complete sincerity, is rather a source of obscure unrest, as well as a negative element for the spiritual commitment of life and action.