SPIRIT. It corresponds to the Greek πνεῦμα and νόος, and to the Latin *spiritus* and *mens*. Etymologically it means “breath,” “puff” (to which are related the expressions “vital spirit” and “animal spirit” used by Bacon and Descartes [v.]), and thus presents a derivation analogous to that of *anima* (soul) [v.]. Used as a synonym of *anima*, it signifies the vital principle in general; but often it is identified with the rational soul (e.g., in Scholasticism, in Descartes, in Leibniz [Monad., 82-83]) or even with thought [v.], and then it is opposed to the sensible. In a derived sense one speaks of the spirit of a doctrine, of a book, etc., to indicate the central idea or animating principle, which often stands in opposition to the “letter.”
In Plato and Aristotle, *spirit* begins to acquire the sense of an immaterial, incorruptible, and immortal essence, although uncertainties and obscurities remain even in Aristotle himself, who still conceives of πνεῦμα in a materialistic way (something intermediate between body, σῶμα, and soul, ψυχή). For the Stoics, πνεῦμα is subtle matter; in man it is a spark of the divine πνεῦμα or creative reason (λόγος σπερματικός: Stobbe, Ed., 1, 374), which is the active principle, the living universe; yet Seneca (Epist., 65, 22) opposes *spirit* to flesh, and Marcus Aurelius identifies the pneuma or spiritual breath with the incorporeal soul (Ric., II, 2). Neopagans and Neoplatonists sharply distinguish (and this helps to clarify the concept of *spirit*) between body, soul (ψυχή), and *spirit* (νόος), which Plotinus [v.] defines as the unity having multiplicity within itself (Enn., V, 9, 6). Thus *spirit* comes to signify the creative principle.
Apart from the theological meaning it has in the New Testament (especially in St. Paul), Christian philosophy inherits (and enriches) the concept of πνεῦμα as an immaterial vivifying soul distinct from ψυχή (Irenaeus, *Haer.*, V, 12, 2). Origen [v.], who also distinguishes between ψυχή and πνεῦμα, makes the latter the principle of judgment concerning good and evil, truth and falsehood (*De princ.*, III, 1-5); and St. Augustine [v.], who distinguishes between *ratio* and *intelligentia* (inherent to *mens*), identifies *spiritus* with the faculty of forming, combining, and dissociating the *similitudines corporales* (De Gen. ad litt., XII, cap. 23, n. 49), the fruit of the soul’s activity. Instead, when he uses it in the biblical sense (De anima et eius origine, II, cap. 2, n. 2), he does not distinguish it from *mens*. To Christian philosophy are owed the clarification and deepening of the distinction between *spirit* and body and the new, more complex meaning of the concept of *spirit* [V. SPIRITUALISM].
In modern philosophy, on the one hand Descartes makes the spiritual substance (*res cogitans*) the opposite of *res extensa* (*Principia*, I), and Spinoza one of the attributes of the divine Substance, constitutive of its essence, inasmuch as God is *res cogitans* and *res extensa* (Eth., part 2, *De mente*, props. I-II); and on the other, empiricism [v.] identifies *spirit* with the totality of representations and consequently denies that it is a substance (Hume, *Treatise of Human Nature*, part 4, sec. 5-6). On the basis of Kant’s [V. KANT] concept of the transcendental *I*, whose a priori forms are modes of functioning, transcendental idealism derives from the concept of *spirit* a gnoseological-metaphysical import, opposing it to matter (antithesis between the unity of thought and the multiplicity of the empirical) and to nature (antithesis between the *I* as creator and created things, between the *I* as freedom and necessity). *Spirit*, understood as selfhood (Fichte) or as absolute thought (Hegel), the imperial active principle, is the creator of total reality. Only to it belongs immortality, not to empirical selves. With Gentile [v.] Hegel’s pure Thought becomes Thought in act, the dialectic of thinking and thought. And thus the concept of spiritual substance is destroyed, and *spirit* conforms to nature. The term *esprit* still has its own meaning in Pascal [v.] as a multiplicity of cognitive perspectives (gnoseological pluralism) or of special aptitudes: *esprit de géométrie*, *esprit de finesse*, etc. (*Pensées*, ed. Brunschvicg, 1-4).