Life

LIFE. - I. PHILOSOPHY. - 1. Notions. In contemporary philosophical language, "life" indicates, in the strict sense, "a set of phenomena (particularly: nutrition and reproduction) proper to beings endowed with a certain degree of organization." By analogy this term is applied to certain super-individual structures that, on the human plane of the "objective spirit" (objektiver Geist), in the Hegelian sense or in the less systematic sense of the Geisteswissenschaften, manifest an activity of self-organization and irreversible transformation: growth and death; thus the "life" of artistic forms, of civilizations, of societies, of language. From a phenomenological point of view, three degrees of determination of the living being are distinguished: a) the empirical-pragmatic degree of common sense; b) the empirical-scientific degree of the biological sciences; c) the properly philosophical degree (v. BIOLOGY and infra, II).

Despite the difficulty of recovering, beneath the cultural evolution of concepts, the original aspect, and despite the confusion of empirical concepts, the convergent data of ethnological investigation and of the psychology of infantile perception lead one to affirm that man has the original tendency to consider all bodies as living and endowed with intentions (cf. Piaget, La représentation du monde chez l'enfant, Paris 1926, p. 160). Thus animism and anthropomorphism would determine the two components of the primitive empirical concept of life: spontaneity of movements and their intentional expression; as well as the primitive "place" where we perceive them, the human world, which according to some would be the first to be grasped (cf. L.-A. Feuerbach, Grundsätze der Philosophie der Zukunft, Leipzig 1846, § 32 p. 231). This affirmation is taken up by some existential philosophers (e.g., M. Buber, who in Ich und Du, French trans., Paris 1938, p. 50, distinguishes between a general "animation" of the world and the instinct of cosmic relation that makes things a "thou" as opposed to a "that" of interested and scientific investigation). Therefore: human world, animal world, vegetable world, inorganic world, in the opposite sense of the ascending ontological hierarchy which does not necessarily coincide with the phenomenological order (cf. H. Bergson, Essai sur les données immédiates de la conscience [Paris 1936, p. 108], for whom the idea of inertia, because it is the negation of spontaneity, is genetically simpler than the latter).

The origin of this perception of life (a question intimately connected with that of the perception of the psyche of others) has been explained both by a "sensitization" (Einfühlung) that projects into things our own "life" (on the theory of Einfühlung, cf. Th. Lipps, Aesthetik, p. 355, in Die Kultur der Gegenwart, VI, part 1, Berlin 1907); and by an induction that, from the analogy of expressive motions, concludes with a similarity of animation; and as Scheler wishes to explain it, who seems to admit it both for the application of the "vital centers" (Vitalzentren) and for that of the "spiritual centers" (Geistzentren; cf. Wesen und Formen der Sympathie, 5th ed., Frankfurt am Main 1948, pp. 252-87, esp. p. 255 ff.), through an a priori of an almost emotional order (irreducible to an innate idea and to a properly so-called intuition) that immediately reveals, in an organic and expressive tonality, the vital sense of these motions. In conclusion, an "immediate" apprehension of the living being seems more probable, grasped as a "concrete significant totality" (St. Thomas attributes it to the "cogitative" power; cf. in De Anima [ed. A. M. Pirotta, Turin 1925, n. 396]) where the central phenomenon is the movere seipsum, according to the various functions of life. The specific concept of vegetative life is relatively late. Some ethnologists hold that attention to the life of plants developed particularly in the civilizations of the matriarchate (v.).

2. History

a) Ancient philosophy. - In ancient philosophy three principal orientations are distinguished: a cosmic conception of life, an anthropological conception, and a more expressly biological representation. The first, represented above all by Heraclitus (and taken up by Stoicism), envisages a "cyclic" becoming (ἐπὶ κύκλου; H. Diels, Vorsokratiker, 6th ed., Leipzig 1910; B. 103) animated by an "ever-living fire" (πῦρ ἀείζων; ibid., 30) whose terms are susceptible of reversible transformations according to a law of unity and return.

For Stoicism the entire world and its evolution form a living being; "the becoming of being is analogous to the evolution of the living being" (cf. E. Bréhier, La théorie des incorporels dans l'ancien stoïcisme, 2nd ed., Paris 1928). Being is assimilated to a "seed," which, developing by virtue of an immanent causality, configures it into a definite structure (on the Stoic terminology relating to life cf. G. Kittel, Ζάω, in Theol. Wörterb., II, pp. 838-39; on the classical usage, pp. 833-38). The anthropological conception is affirmed with Plato, for whom the world is also a "perfect animal" (Tim. 23 d), similar to its intelligible paradigm (ὅμοιον τῷ παντελεῖ ζῷω, ibid., 31 b). But the "logos" is here more manifestly assimilated to a "νοῦς" that informs it (Phil. 30 d). And the world of immutable Ideas seems to him himself to be animated by a kind of internal δύναμις that has been able to suggest a complete assimilation of the Ideas into the souls thought of as living. Being is οὐκ ἄλλο τι πλὴν δύναμις (Sophist, 247). In the opposite sense A. Diès affirms (La définition de l'être et de la nature des Idées: le Sophiste de Platon, Paris 1932, ch. 2), that the tendency to define life by means of intelligence and not only on the human plane is already clear. But it is above all in Plotinus that every form of life is ἐνέργεια (Enn., III, 11, 16, 17, 18, ed. E. Bréhier, Paris 1927); this "energy" is, however, itself an obscure concept: πᾶσα ζωὴ νόησις τίς (Enn. III, VIII, 8-17). The degrees of life are therefore the same as the degrees of thought, of an ever clearer thought. Contemplation is life par excellence (Enn. III, VIII, 8, 26-30); and, to tell the truth, all beings are "contemplations": θεωρίας τὰ πάντα ὄντα (ibid. 26). But the Good from which life springs is not living (Enn., VI, VII, 15,

Barlaam and Josaphat (v.). Reliefs by B. Antelami in the lunette of the southern door (ca. 1200) - Parma, Baptistery." loading="lazy" />

19-20). Aristotle's merit is to have elaborated a strictly "biological" conception of life. He does indeed accept from Plato that the highest life is "contemplation" and his God is ζῷον ἀΐδιον, identity of intellect and intelligible, ζωὴ ἀρίστη καὶ ἀΐδιος (Metaph., XII, 7, 1072 b 15-30). But his originality in elaborating the concept of ψυχή is expressed in the following three points: insistence on the strictly "vegetative" aspect of the living being (in its principal phenomenon: nutrition), which is its common denominator, opposing both the rationalistic reduction of the soul to knowing (400 b 16-24; 411 b 27-30) and its reabsorption into local motion and the "elements" (ibid.); appeal to the positivity of experience, or the "physical" method, which, in order to determine the nature of the soul, begins by starting from "functions" and "operations" (403 b 5-10); accentuation of the unity of the living being through the substantial immanence of the soul in its matter: for which reason he rejects, as meaningless, the problem of the "union of soul and body" (412 b, 6-9, 19-20); the principle of the hierarchy of forms, inasmuch as the higher soul as substantial form includes the lower forms and is not added to them (414 b 1 ff.); it is uncertain, however, whether Aristotle made express application of this principle in the case of the human soul (cf. AVERROES; ST. THOMAS AQUINAS, saint).

b) Christian philosophy. - In the writings of the New Testament (St. John and St. Paul) the philosophical elements concerning the conception of life are the following: a) affirmation of life in God, whose perfect immanence, independent of the freely created cosmos, unfolds in the Trinity of Persons (Aristotle's God is alone); b) intimate connection of life, lux, amor; ζωή, φῶς, ἀγάπη (the latter is missing in the classical conception of divinity); c) exercise of the Christian life through faith and charity; d) hierarchy of the degrees of life: the carnal man, the rational man, the spiritual man (guided by the spirit of God): σῶμα, ψυχή, πνεῦμα (I Thess. 5, 23); ψυχικὸς ἄνθρωπος, πνευματικὸς ἄ. (cf. F. Zorell, ἄνθρωπος, in Lexicon graecum N. T., 2nd ed. Paris, 1931): a hierarchy taken up again by Maine de Biran (cf. Nouv. Essais d'Anthr., ed. P. Tisserand, Paris 1949, XIV, pp. 195-402). It is St. Thomas's merit to have fused these elements in the Christian conception of life with Aristotelian philosophy; a) phenomenological: the "relevant" character of the living being is the movere seipsum which manifests itself immediately in the behavior of the animal through a concrete apprehension reserved to the sense that is "intentional" par excellence: the cogitativa (v. and cf. Sum. Theol., 1a q. 18, a. 16; q. 16; 2nd in de An., ed. Pirotta, nn. 396-98); b) ontological: inasmuch as life actualizes the immanence of acting ordered ex se toward the perfection of the Agent; c) through this immanence intensified by an "interior fecundity," life attains the sphere of perfections "simpliciter simplices" susceptible of analogical modalities and applicable to God (Sum. Theol., 1a, q. 16, a. 2). Hence an ascent of ever more perfect life that unfolds from vegetative immanence to the intimate life of the Trinity (v. Contra Gent., IV, 11).

c) The philosophy of the Renaissance returns to the Stoic conception that considers the world as "a great animal"; vital energy, according to a naturalistic mysticism (represented by the names of Paracelsus and Bruno [v.]), unfolds in all the manifestations of the cosmos.

d) Modern philosophy reacts against this panvitalism with mechanism, which has its systematic structure in Descartes: he substitutes "mind" for the soul of the ancients (Oeuvres, ed. A. Tannery, VII, Paris 1905, p. 356) and presents the paradoxical theory of "animal-machines" applied to the human body itself (ibid., XI, 223 ff.; Traité de l'homme, ibid., p. 120 f.; Traité des Passions, ibid. pp. 330-31), a theory taken up again by Malebranche (Recherche de la vérité, V, ch. 3, cf. also H. Bousson, La religion des classiques, Paris 1948, ch. 7) and which found its radical expression in the theory of the "man-machine" dear to the physicians and materialist philosophers of the 18th century (La Mettrie). Leibniz attempts a compromise between Aristotle and Descartes. The world, without having a soul (cf. Leibniz, Textes inédits, ed. J. Grua, Paris 1910, p. 558), is full, in its smallest parts, of vital principles or entelechies (Considérations sur le principe vital, in Opere varie, Ital. tr., Bari 1912, pp. 75-83), immortal because indivisible, endowed with confused perception and appetition, without influence on the world of bodies: hence a new dualism in the dubious realm of final causes (the world of life) and efficient causes (the world of bodies and of mechanism), which pre-established harmony makes agree extrinsically. This psychic spontaneity, whose freedom is a particular case (cf. Textes inédits, ed. J. Grua, p. 287 f.), is closely linked to the thesis on substance-force, on "conatus" (cf. L. Jalabert, La théorie leibnizienne de la substance, Paris 1947, chs. 1-3). For Kant the finality immanent in the living being, in opposition to aesthetic and hedonic finality, is objective, that is, referred to things (Kritik der Urteilskraft, Leipzig 1948, p. 161); it is material or real and not merely formal as that of geometric figures (§ 62); it is intrinsic in opposition to the extrinsic finality of a means in the service of man: since organized beings are for themselves "ends of nature" (Naturzwecke, § 65), cause and effect of themselves (sich bildende Kraft), causa sui.

e) Modern philosophy. - Hegel tends to reconcile the two aspects of finalism and mechanism as the two aspects of necessity and freedom (cf. Logik, ed. G. Lasson, II, Leipzig 1945, p. 387). In the Hegelian conception life presents three aspects: a) theological-religious (in the Theologische Jugendschriften): life implies interiority in opposition to the exteriority of the law and to the master-servant dualism, which are the characteristic of the Old Testament (ibid., pp. 4-16); an interiority that expresses the law of love and the relation of the Father to the Son, proper to Christianity, through freedom. b) logical-dialectical: life is the immediate form under which the Idea appears (Logik, ed. cit., vol. II, p. 412), inasmuch as dynamic subjectivity: end and cause of itself. Life presents three moments: the living individual as constituting subjectivity and organizing self-determination of its matter; the constituted individual whose properties are sensibility, irritability, reproduction, a vital process that unfolds a relation in the exterior environment which the living being destroys by assimilating it, need and impulse (Bedürfniss and Trieb) which are completed in appropriation; genus (Gattung) which inserts the individual into a chronological series and makes it a member of a species in which it participates (ibid., 426 ff.; ed. Encykl., § 369-70). c) phenomenological: life as interiorization of its object is "reflection" on itself and constitutes the first stage toward the Selbstbewusstsein under the form of desire for itself, negative because destroyed by its object (Phaenomenologie des Geistes, ed. W. Hoffmeister, Leipzig 1948, p. 135 ff.). The Romantic conception of life has as its principal representatives Schelling, Schopenhauer and Nietzsche. Schelling conceives the living being as the foundation of itself, causa sui, by reason of the necessary relation of the parts in the whole and of the whole in the parts, and therefore it presents itself as an immanent concept (inwohnender Begriff) in which matter and form are inseparable (Ideen zu einer Philosophie der Natur, in Schellings Werke, I, Leipzig 1907, p. 134 f.): unity of nature and of freedom, of necessity and of contingency, of mechanism and of finalism. The soul, the principle of life, cannot be either a force or a juxtaposition of forces, since it must harmonize these forces, but a spirit (Geist als Prinzip des Lebens gedacht heisst Seele, ibid., p. 147). This principle, common to all living individuals, is not proper to any one of them, just as the spirit itself is infinite and absolute and limits itself, by means of the force of a negative principle of individuation, in the variety of species and of individuals (Von der Weltseele, ibid., p. 599). Consequently it is called: « Gemeinschaftliche Seele der Natur » (ibid., p. 665), and the same taken as a whole is an « allgemeiner Organismus », a whole in which inanimate bodies are « extinct lives » (erleuthenes Leben). The essence of all things is therefore life (ibid., p. 596). And life itself is nothing but the manifestation of this creative genius, immanent (Ideen, p. 322) in its work in the universe and which we can recognize by means of an « intuition » (Anschauung). Schopenhauer rejects the Weltseele because it implies a consciousness and a knowledge that do not belong to all beings (Die Welt als Wille und Vorstellung, in Schopenhauers sämtliche Werke, ed. J. Frauenstädt, III, Leipzig 1873, p. 398); life is at once the immediate and fundamental object of the will of the noumenon (Wille zum Leben, Drang und Trieb zum Dasein) and the core of reality: from this the world originates, and one of the objectifications of this will of the noumenon, whose first degree is the inorganic world (ibid., II, 1873, chaps. 17-29). The living being differs from the inert one in that the latter exhausts in a single stroke the law it expresses (thus the falling stone adequately explains gravity; ibid., II, chap. 28, p. 185); the plant or the animal, on the other hand, is inadequate to the specific idea it tends to express, and while the former is subject to the equality of action and reaction that governs causality, the living being manifests a reaction absolutely disproportionate to the « stimuli » that provoke it (ibid., II, chap. 23, pp. 137-38; on the distinction between Ursache, Reiz and Motivation cf. also Über die Freiheit des Willens, Sämtl. Werke, cit., IV, ibid. 1874, p. 29 ff.). Hence in the living being there is a plasticity, an individuality, a spontaneity (Über den Willen in der Natur; Sämtl. Werke, IV, pp. 60-64) that lends itself with greater difficulty to the rigidity of mechanical and mathematical laws although, nevertheless, their necessity is present in it. Ed. von Hartmann joins Schopenhauer's unconscious will with the unconscious idea in a single principle that is called the Unconscious (Philosophie des Unbewussten, French trans., I, Paris 1877, p. 5), an idea without which this will would be empty and without object (ibid., p. 33). This unconscious manifests itself in the life of the body as in the human spirit: but it is above all clear in the organism under the form of organic finalism. Nietzsche in his essay on the « transvaluation of all values » gives to life an axiological sense of the supreme value. Far from denying itself, as in Schopenhauer, life must, under the form of « will to power » (Wille zur Macht), affirm itself against all the degenerating tendencies that he attributes to civilization and to Christianity. Such a will to power already affirms itself in the inorganic world under the form of a conflict of forces (Wille zur Macht, I, Paris 1909, pp. 296-98); more clearly in the organic world as a struggle of individuals and of species; in the human world under the form of science (ibid., pp. 274-275) and of power, and under a more concealed aspect in morality itself (ibid., pp. 339-50); life and will to power are synonyms of intense energy. Idealized as the supreme value, the will to power, which is life, finds in Zarathustra the symbol of the « perfect living being », the « superman » (« Übermensch », cf. Also sprach Zarathustra, book III, Paris 1946, p. 227 ff.). In positivism, A. Comte intends to free biological phenomena from theological interpretations (by means of arbitrary will) and metaphysical ones (by means of an individual or cosmic psyche) in order to subject them to the positive requirement of explanation by means of laws. Thus explained, the biological phenomenon is summed up in the correlation of two elements (Discours de philos. posit., III, Paris 1908, p. 141 ff.). H. Spencer, preoccupied with the problems of genesis and dominated by the idea of evolution, starts from the concept of "force" (as the unknowable substratum of all cosmic phenomena). Plants and animals are transformations of force through the integration of matter and the concomitant dissipation of motion. Evolution is nothing other than "the change from an incoherent homogeneity into a coherent heterogeneity as a result of such integration and dissipation." Dissolution follows the reverse path (cf. First Principles, French trans., J. Cazelles, Paris 1871, ch. 6).

According to Bergson, the essence of life is the "creative duration" that can be grasped through an intuition; life presents itself as a "whole" irreducible both to an extrinsic finalism and to an intrinsic finalism limited to a single organism (given that in nature there is no absolutely clear-cut individualism). But if the whole is original and is not reduced to an integration of parts, as Spencer believed, what sends us back from mechanism to a constructive finalism is an original vital impetus (élan vital), a simple movement whose evolution is not accomplished in the successive stages of one and the same tendency (vegetative, inactive, rational life), but in three divergent directions. The plant, the animal and man are the three divergent directions of an activity that has split apart as it developed (Évolution créatrice, Paris 1946, pp. 1-7).

3. Critical discussion

One observes, particularly in contemporary philosophies, a shift of accent from the ontological to the axiological, insofar as life, understood as a principle, tends more and more to be interpreted as value. Hence the affective-axiological resonances of the term. Such divergences may cast doubt on the unity of the concept of life: nevertheless, brought back to its original characteristic, life has suggested to philosophical speculation the following aspects: a) first of all the immanence of acting (rather than the spontaneity valid for every natural action, cf. the observations of C. Fabro on the work of F. De Sarlo, Vita e Psiche, in Bollettino filosofico, 3 [1937], pp. 65-77), so well brought out by St. Thomas; b) then, or consequently, causality, whose "schema" is the organism in the embryonic phase (on biological schemata in Aristotle, cf. H. Donovan-Hantz, The biological Motivation in Aristotle, New York 1937); c) fecundity (admirably developed by St. Thomas in Contra Gent., IV, 11); such a structure of the concept of life, brought back to its intelligible degree, by no means excludes, but rather implies, the affective-axiological characters clarified by the Romantic philosophies and by the contemporary Lebensphilosophien.

BIBLI: W. ROUX, Der Kampf der Theile im Organismus, Lipsia 1881, p. 351 sg.; J. B. Lamarck, Philosophie zoologique, Parigi 1907; F. Raffaele, Individuo e specie, Salerno 1910; R. Berthelot, Évolutionnisme et platonisme, Parigi 1912; A. Cournot, Essai sur les fondements de nos connaissances, ivi 1912, cap. 9; J. v. Uexkull, Clavell und Innenwelt der Tiere, 2ª ed., Berlino 1921; H. Rickert, Philosophie des Lebens, 2ª ed., Tübingen 1922, cap. 1; L. Klages, Vom kosmogonischen Eros, 2ª ed., Jena 1926; vari autori, Cahiers de philosophie de la nature, ivi 1929-35; Ed. Le Roy, L'existence idéoliste et le fait de l'évolution, Parigi 1929, Introduction; X. Manquat, Aristote naturaliste, ivi 1930; N. Hartmann, Das Problem des geistigen Seins, Berlino 1933, p. 90 sg.; G. Singer, Histoire de la biologie, trad. franc., Parigi 1934; F. Ravaisson, Testament philosophique, ivi 1935; J. Boyer, Essai d'une définition de la vie, ivi 1939; G. De Ruggiero, Filosofi del Novecento, Bari-Laterza 1946, p. 41; R. Ruyer, Éléments de psychobiologie, Parigi 1946; W. Dilthey, Le monde de l'esprit, I, ivi 1947, p. 130 sg.; F. Grégoire, Note sur la philosophie de l'organisme, in Revue philos. de Louvain, 1948, p. 278 sg.; H. Salman, La nature du vivant, Parigi 1948; R. Dalbiez, La méthode psychanalytique et la doctrine freudienne, I, Parigi 1949, p. 207; L. Lévy-Brühl, Carnets, ivi 1949; N. Hartmann, Philosophie der Natur, Berlino 1950, parte 3ª, cap. 45-64; A. Brunner, Der Stufenbau der Welt, Monaco 1950, p. 549 sg.; J. Ortega y Gasset, Obras completas, II, Madrid 1951, pp. 451 sg., 149 sg.; III, ivi 1951 pp. 270-80; A. Wenzl, Metaphysik der Biologie von Heute, 2ª ed., Amburgo 1951; E. Dupréel, Vers une théorie sociologique de la vie, in Revue philosophique, 1952, pp. 351-68.

Stanislao Breton

II. ORIGIN OF LIFE

1. Characteristics of the living being

There is unanimous agreement in recognizing that differences exist between inanimate bodies and living beings. These, however, do not concern the material elements of either, since it has by now been demonstrated that organisms are constituted by the same elementary substances that form a great part of the inorganic world: carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, calcium, sodium, potassium, magnesium, with traces (often of very important function) of iron, iodine, zinc, copper, manganese, cobalt, rubidium, etc. Nor do the individual molecular aggregations that these atoms assume in the living being, although they are much more complex than what is found in inorganic nature, seem to mark in themselves, as was once believed, a characteristic of the living being, since such compounds can, at least theoretically, be produced in the laboratory, as has already happened for some. Thus Wöhler (1828), by heating cyanic acid and ammonia, obtained urea identical to that which 19 years earlier Rouelle had found in the urine of mammals; thus, a few decades later, Kolbe carried out the synthesis of acetic acid, Berthelot that of fats; thus, at the beginning of the century, Fischer obtained the synthetic formation of polypeptides, and recently Betti succeeded in manufacturing by synthesis those optically active compounds that nature presents to us as such, but that our syntheses had until then produced only as racemic products, that is, as a mixture of the two dextrorotatory and levorotatory compounds. We are of course very far from having reached, by artificial means, the complexity of organic molecules; but, theoretically, nothing prevents us from arriving there.

The radical differences derive from the fact that even the most elementary organisms feed, grow, reproduce, are irritable, age, die, whereas nothing of the kind is encountered in the inorganic world. The organism feeds by intussusception, attracting to itself heterogeneous material particles, transforming them, through a long work of molecular decomposition and recomposition, and impressing upon them its own specific structure. In this way it increases its volume, if it has not yet reached the adult stage, up to a limit characteristic of the various species; at the same time it differentiates its individual parts with cytological and anatomical formations of very diverse structure, and establishes an incessant material and energetic exchange with the surrounding world. Once adult, and sometimes even in juvenile stages, the unicellular as well as the multicellular organism is always capable of giving origin to other individuals of the same species, by dividing itself into two or more nearly equal fragments, or by delegating this function to particular cells whose sole task is to transmit life.

It is sometimes objected that crystals present some analogous manifestations. Like the living being, the crystal too is born from the mother liquor, grows by attracting to itself other particles of the dissolved crystallizable substance; in this growth, the particles do not assume the indifferent and chaotic position of vitreous substances, but, just as the cells deriving from the fertilized egg take in the embryo positions that are well fixed for each species, so in the crystal atoms and molecules arrange themselves with admirable order, giving rise to geometric figures characteristic of the various bodies. And other analogies. In reality there is no real similarity between the two series of phenomena. The birth, if one wishes to call it so, of a crystal of calcite, for example, occurs when, in a solution of calcium carbonate, some molecules are the first to assume the rhombohedral spatial arrangement. No chemical reaction takes place: it was calcium carbonate in the solution, it remains calcium carbonate in the crystal: what is new is only the form, insofar as it is the spatial arrangement of the molecules. And already, from this moment, one is in the presence of a perfect calcite crystal, which increases its volume, without limits, by attracting along its edges and faces other identical elementary crystallites of calcium carbonate, not derived from it nor transformed by it, but formed in the mother solution. And in growing, rather than acquiring heterogeneity or a new form, it merely makes visible the submicroscopic form of the primitive lattice. Not therefore an individual that grows and builds itself, as in the living being, but new identical elements that, without losing their own nature or their own individuality and without acquiring anything from the union, superimpose themselves one upon the other according to well-defined laws, thus causing the volume of the whole to increase.

Every organism, after a certain period of existence, characteristic of the various species, ages and dies, whereas nothing similar happens even in crystals, which nevertheless represent the highest manifestation of the activity of inorganic matter. Nor are microscopic beings and the germinal cells of higher living beings an exception to this law, since even in these cases the original individual passes away with time, although a part of its matter lives again in the offspring.

Another characteristic of the living being is irritability, defined by Cl. Bernard as the property of the "living element to act according to its nature under an external provocation" (Leçons sur les phénomènes de la vie communs aux animaux et aux végétaux, Paris 1878, p. 248). It comprises all the phenomena by which living beings react to excitations coming from external factors, such as light, gravity, electricity, contact with a mechanical body, air, water, humidity, chemical substances, etc., and differs from the activity of inorganic matter, in that the reaction with which the living being responds to an external excitation is, each time, elaborated by the living being itself, and is therefore variable from organism to organism, from physiological moment to physiological moment; and if, for a stimulus to act, a minimum of intensity is required, once a certain limit is exceeded the organism either no longer reacts or reacts in a sense opposite to the stimulus.

2. Origin of life

If, in recognizing that the above-mentioned operations are characteristic of the living being, the agreement is universal, great indeed are the divergences among scholars in the way of interpreting them and, consequently, in the problem of the first origin of life.

Some still consider plausible the hypothesis of coanozoa or of interastral panspermia, put forward by Richter (1865) and later shared by eminent scientists such as W. Thompson, Helmholtz, Van Tieghem, Bonnier, Arrhenius and others, who also sought to resolve the grave difficulties of a physical and biological order connected with it. In brief, the hypothesis maintains that life established itself on earth by means of germs coming from other stars, already inhabited. It is superfluous to examine whether those difficulties are really resolved by the explanations attempted by the various authors; the fact is that the problem of the first origin of life is not solved, but simply shifted from the earth to that or those stars from which it is supposed to derive.

The materialists affirm that life originated on our earth by spontaneous generation from inorganic matter, as it is customarily but improperly called. Already Empedocles, Democritus, Aristotle and other philosophers among the Greeks; Lucretius and Virgil among the Latins and, in some manner, St. Thomas himself and ancient Scholasticism upheld the same doctrine, and everyone knows that, until 1600, it was peacefully accepted, it being held that such autochthony continued to occur, at least for the lower organisms. The affirmation of the materialists thus seemed proven. Except that Fr. Redi (Esperienze intorno alla generazione degli insetti, Florence 1668) began to demonstrate that the worms developing from putrefied flesh do not originate spontaneously, but rather from eggs laid there by flies; A. Vallisneri (Storia della generazione dell'uomo e degli animali, Venice 1715), together with Malpighi, demonstrated that the larvae present in galls and in the pulp of fruits also derive from insect eggs; Spallanzani (Osservazioni e sperimenti intorno agli animaletti delle infusioni, Modena 1765) extended the same demonstration to the infusoria, discovered a century earlier by Leeuwenhoek; and finally Pasteur proved (1860), against Pouchet, that even microscopic bacteria do not derive from inorganic matter but from pre-existing bacteria.

With these observations, the demonstrative proof of spontaneous generation thus came to be lacking, and the materialists, in support of their thesis, had recourse and still have recourse to attempts to manufacture life in the laboratory, to filterable viruses (v.) and to other presumed organisms still simpler which, at the beginning of life, would have originated from inorganic matter. But the attempts to manufacture life have always and only led to the construction of inanimate toys; the primordial existence of organisms simpler than viruses is a pure presumption not supported by any factual datum, and devised for the sole purpose of saving the thesis; regarding viruses it is still debated whether they are living, whether they are authentic organisms or fragments of organisms, there is no proof of their spontaneous origin, while their parasitism, rigorously obligatory, excludes in any case that they could have been the first living beings. In conclusion, so-called spontaneous generation, the foundation of the materialist hypothesis, has no experimental proof at its disposal, and all those that exist are contrary to it.

C. E. Guye (L'évolution physico-chimique, Paris 1922) and Lecomte du Noüy (L'homme devant la science, ibid. 1939) have also calculated mathematically the probability of the chance formation of a single protein molecule, much simpler than those actually found in living beings, reaching the conclusion that it is theoretically so improbable as to be practically impossible, as, for example, the spontaneous formation of a watch is practically impossible, even though it is far from having the complexity of a living being.

Among the mechanists, for whom organisms are to be likened to machines constructed by nature, some are materialists and thus the observations made above and those that will be made later apply to them; others are more or less openly theists and, while denying that in the living being there are principles other than the chemical-physical forces of their material constituents, they admit, with Descartes, that the power of God intervened to form these most perfect machines, effecting those chemical combinations and physical aggregations that the chance of the materialists cannot produce. All the difficulties raised by spontaneous generation disappear in this view. But if it escapes the difficulties concerning the origin of life, it then fails to explain adequately the intrinsic unity proper to every organism, as it manifests itself through its operations.

The vitalists likewise admit that, at the origin of life, there was a direct intervention of God, but not restricted merely to forming certain highly improbable chemical combinations, but rather extended to endowing the first organism or organisms with principles different from and superior to the physical-chemical forces which, alone, operate in the inorganic world. A doctrine already upheld by ancient naturalists, such as Aristotle, taken up again by Scholasticism and revived in modern times, chiefly through the work of Driesch; a doctrine which, both in the origin of life and in the operations of living beings, does not deny the importance of matter; it denies that matter alone is sufficient to produce life or to explain its characteristic activities.

Great is the repugnance of scientists to accept that there exist in the living being principles and forces different from the physical-chemical ones that can be measured with suitable instruments; and yet, if one wishes to grasp the fundamental element that characterizes life, one is compelled to do so in the name of that logic from which even the experimental scientist cannot prescind.

3. Essence of life

For whoever considers with absolute objectivity the development and the manner of operating of any organism whatsoever must admit a coordination, subordination and convergence of its most varied activities toward the good of the whole. Every organism, despite the countless number of cells that perhaps compose it, presents itself as a natural unity, in which the individual parts, macro-or microscopic, lose their autonomy, merging into the great harmony of the whole. To fix the concepts better, it is appropriate to point out some fact in a multicellular organism, where the phenomena unfold with greater evidence.

In fertilization, which marks the beginning of a new life, this new natural unity is constituted. While in the divisional process of a cell the chromosomes split longitudinally, migrate in a double row to the opposite poles of the nucleus, and the membrane, constricting, divides cytoplasm and nucleus into two roughly equal halves; in fertilization, on the contrary, the paternal and maternal germ cells mix their cytoplasms in an inseparable manner, the respective chromosomes pair up two by two — chromosomes which, almost in view of this fusion, had halved their number — they become covered with a single cellular and nuclear membrane, immediately giving the impression that from two elements derived from different organisms a single cell is constituted. Even more, it already encloses, in potency, the entire future organism and that determinate organism. To actualize it, it will have to multiply itself innumerable times and gradually differentiate the parts that will be forming; but normally nothing will happen that is not already, in some way, contained in it, nothing that does not feel its influence. From the external environment it will demand nourishment and oxygen to grow and produce the necessary chemical reactions, but above all that it not hinder its course nor slow down its evolutionary impetus. This impetus is inherited by the first blastomeres derived from the fertilized egg. They too grow larger and, having reached a determinate size, divide in their turn, but always transmitting to the daughter cells the same urge to actualize the complete future organism. Morula, blastula, gastrula, are successive stages of this incessant journey in which the cells, ever more numerous, continue to cooperate for the attainment of the single end. And as previously each of them, so now each group has a well-defined function to perform, and if one becomes incapable of it, its task is assumed by cells of another sector, so great is the common anxiety to fulfill the mission entrusted to them, almost in solidum, by nature.

Every cell nourishes itself, and the intake of materials takes place through the membrane. Now, the permeability of the membrane is certainly conditioned at every instant by its physical state and by the chemical equilibria existing on its two faces. But it is well known that those conditions vary incessantly, and not by chance, so that the permeability of the membrane varies continuously in quality and quantity, now permitting the entry of substances that previously it did not allow to penetrate, and permitting it to the extent that they are necessary or useful, not to it alone, but to the entire cell. Indeed, this intrinsic selective power goes beyond the needs of the cell, aiming also at the needs of neighboring and distant cells, and extending even to the future needs of the organism in formation.

The living being thus comes into being gradually, through a self-construction from within and a dominion extending in space and time over an ever vaster matter, which assumes living properties and cooperates in producing those organo-formative substances that do not create life, but are produced by life and used as means for new constructions. In this intense labor, of which every biologist is aware, one discerns, along with the instruments, the matter employed and the succession of the different structures; yet one cannot succeed in identifying the element that coordinates and orients phenomena so disparate and numerous, now exalting and now depressing the activity of the individual parts so that the whole may be built progressively and harmoniously. And yet this directing cause must exist, since its effect exists, and it must be intrinsic to the organism itself, if one does not wish to resort to a useless occasionalism with all the difficulties connected with it.

This unity, in its various aspects of coordination, subordination of parts, and convergence of activities toward the good of the whole, is still found in the adult, despite the fact that its cells do not form a true material continuity. To mention but a few facts, one recalls how the different reactions composing a given metabolic cycle do not as a rule take place in the same site, but, begun in one organ, are then completed by others to which the intermediate products manufactured by the first and still unusable by the organism arrive through the blood. One recalls how alterations that perhaps affect only a very limited region make themselves felt in the whole, and how it is still the entire organism that intervenes, through the activity of numerous of its parts, to reestablish equilibrium.

There is then a phenomenon which, while on the one hand it confirms the unity of the living being, on the other opens a chink onto the intimate nature of this property, making it clearly glimpsed as due to something that is not reducible to matter alone: the individual's preserving itself equal to itself, inasmuch as it is always the same organism, despite the incessant modifications of the physico-chemical state of its parts and the continuous material replacement of their constituents. All the matter present in it at a given moment is transformed and replaced by other matter: and yet the individuality of the organism remains constant until its death, and man has full awareness of this fact.

Finally, the unity of a living organism becomes, by contrast, clearer in the coordination and subordination of its parts when one considers the phenomena that occur in "in vitro" cultures, by which one succeeds in keeping alive a fragment of tissue removed from the same organism. These cells, previously so solidary in their operations, so sensitive to alterations affecting one of them, now become entirely independent and are transformed into so many individuals, in which one no longer finds any conspiring toward the attainment of a single end, any mutual collaboration. If one pricks one of them with a needle, it alone reacts amid the total impassivity of its neighbors. Once the purpose of their function and of their differentiation has ceased, they lose both, often transforming themselves into structurally indifferent cells. And almost as if to make more manifest the independence acquired through separation from the whole, they also move apart spatially from one another, each emigrating on its own account toward the edges of the slide, where, with no further restraint or precise purpose, they resume proliferating autonomously, exactly as a single-celled individual would do.

Such is the biological reality that presents itself to anyone who confronts the problem of life. The researcher finds himself before beings formed by one or by billions of cells, constituted in turn by an astronomical number of atoms and molecules such as are also found in the inorganic world, but here operating as parts of a whole that, through them, orderly and finalistically constructs itself, just as orderly and finalistically, once adult, it carries out its various functions. Hence the need for a real principle, different from the physico-chemical forces of the individual inorganic bodies of which the organism is formed, and of an order superior to them, since it is capable of regulating their activity and unifying their action, making of the organism a whole from which the manifold functions derive and for whose well-being they are carried out. It is precisely to this element that St. Thomas's definition refers when he says that life is the intrinsic principle of immanent action.

It is the task of philosophy, and not of science, to investigate the nature of this principle and how its union with matter comes about; but it is the duty of the biologist to admit its existence, since it is an integral and principal part of that biological reality (living organisms) which forms the proper object of his studies.

Giuseppe Bosio

III. LIFE IN ART

In medieval sacred art one often encounters allegorical representations of human life, with which the intention was first of all to express in various figurative ways man's inevitable progress toward death.

In the Cathedral of Torcello, in a Byzantine-style marble bas-relief of the 11th century, set into the stairway of the ambo, a youth with winged wheels at his feet and a balance in his hand signifies the fleetingness of life and therefore of Time (v.). A more complex figuration is found in the lunette of the southern door of the baptistery of Parma, sculpted by Benedetto Antelami (v.) around 1200, depicting the tree of life according to the Buddhist legend of Barlaam and Josaphat (v.). Here a young man, reclining among the branches of a tree, tastes the honey gathered in a honeycomb, unaware that at the foot of the tree two little animals (mice or moles?) are gnawing its roots and a flame-spewing dragon awaits his fall. At the sides the Sun and the Moon, within discs with their respective chariots, represent the passage of time. A similar depiction, with slight variations, is also found in the 14th-century bas-relief on a jamb of the door of the chapel of St. Isidore in St. Mark's in Venice and in a Gothic panel of the Museo dell'Opera del Duomo in Ferrara, where, alongside the usual symbolic elements, a unicorn also appears. Human life was also depicted with a series of representations of the successive ages of an individual, linked to one another in a kind of synoptic table. A fine example of this kind is in a bas-relief of the baptistery of Parma, by the same Antelami. During the Renaissance the concept of life was expressed in a manner entirely different from that of the Middle Ages. In this connection one recalls the great panel by Lorenzo Costa in the church of St. James in Bologna, where the triumph of life is depicted as preceding the triumph of death.

Witold Wehr