MECCANICISM. — Philosophical theory, or more generally a school of thought, that interprets the world as a great machine and seeks to explain all sensible phenomena solely through quantity, local motion, and the notions derived from them (space, figure, time...), thus excluding any substantial and qualitative diversification and change. Mechanicism extends its attempt at explanation also to vital and psychic phenomena, and in this sense is opposed to vitalism, which recognizes the essential irreducibility of life and the psyche to mechanical elements alone. Even when restricted to the inorganic world alone, mechanicism has had various formulations in the history of human thought and has been connected with other conceptions of nature, from which, however, it must be carefully distinguished. Mechanicism atomism (v.), insofar as it responds to the same need to rationalize and visualize the elements of the physical world. However, not every form of atomism is mechanistic; for example, the atomism of Anassagora and Empedocle and the chemical atomism of the nineteenth century are not mechanistic, since they recognize atoms as endowed with qualities and forces irreducible to one another and distinct from pure local motion. Likewise, not every form of mechanicism is atomistic, as in Cartesian mechanicism, which admits the infinite divisibility of quantity. Mechanicism must also be distinguished from mechanics, or the science of motion, founded experimentally and mathematically by Galileo, Newton, and Lagrange, even though the founders and practitioners of mechanics were often dominated by more or less mechanistic conceptions.
I. ANCIENT M
The first historical formulation of m. is found in the atomism of the Greeks Leucippus and Democritus (fifth–fourth centuries B.C.), of Epicurus (fourth–third centuries), and of the Latin Lucretius (first century: De rerum natura). In opposition to the doctrines of Epicurus and Lucretius, which locate the cause of the motion of atoms in weight, Democritus, according to the fragmentary testimonies that have survived, held that no cause should be assigned for the eternal motion of atoms: “Democritus does not hold that the cause of things that always are should be sought” (Aristotle, Phys., VIII, 1, 252 a 35). For this reason Democritus’s mechanistic thought was brought by F. Enriques (Storia del pensiero scientifico, I. Il mondo antico, Bologna 1932, pp. 148–49) into relation with the concept of inertia, which lies at the foundation of the Galileo–Newtonian mechanics, according to which uniform rectilinear motion persists indefinitely without the intervention of a new force, which would be the cause of acceleration. Certainly, the Democritean conception offers more points of contact with the views of modern mechanics than does the later Epicurean doctrine. Nevertheless, one must not forget the profound difference in logical structure between Democritean m. and modern mechanics, nor between Democritus’s atomism and modern atomic theory. Whereas the modern principle of inertia is the result of the Galilean experimental method, Democritus’s motion of atoms is an a priori assumption, and the coincidence of Democritean m. with the kinetic theory of matter, from Bernoulli to Maxwell, is purely partial and extrinsic. Moreover, although the same principle of inertia in modern mechanics has been interpreted mechanistically by many, following Descartes, with the denial of any reality distinct from the body itself and from its motion, nevertheless, in the very founders of mechanics, such as Leonardo and Galileo, and in a non-mechanistic philosophical interpretation, it entails the existence, in the moving body, of a reality distinct from the body itself and from its velocity: impulse or momentum, which fully realizes in itself the Aristotelian notion of a variable quality (cf. P. Hoenen, Filosofia della natura inorganica, Brescia 1950, pp. 123–31, 149). Thus, whereas the m. of Democritus, as well as all subsequent forms of philosophical m., is essentially linked to the electic metaphysics of ‘identity’, modern mechanics is independent of it; hence, acceptance of the latter in no way entails affirmation of the former.II. MODERN MECHANICISM
Mechanicism, with its fundamental idea that all physical phenomena must be explained solely by elements of shape and motion, was taken up again in the modern age as a reaction against the Aristotelian philosophy of quality, which, especially during the period of scholasticism’s decline, had sought to explain the new data of experience by resorting to an ever-increasing number of occult qualities. The characteristic new element of modern mechanicism is the introduction of the Galilean experimental method and, even more, the increasingly complete and refined mathematical description of the laws of motion, aided by developments in mathematics in the seventeenth century, especially analytic geometry and infinitesimal analysis. From the philosophical point of view, special mention should be Descartes (v.), one of the most rigid and consistent forms, which presents itself as the type of non-atomistic mechanicism in opposition to the atomistic mechanicism of the ancient Greeks, renewed, contemporaneously with Descartes, Gassendi (v.).Whereas rigid mechanicism, consistently with its fundamental conception, denies every active power among bodies and admits no other cause capable of influencing changes in motion than mechanical impact, following the Newtonian theory of universal attraction and subsequently as a result of the development of modern chemistry, more moderate forms of mechanicism became established among scientists, admitting the existence of attractive central forces, affinities, and specific properties of the various atoms, irreducible to elements of shape and motion alone. Nevertheless, despite these partial concessions, the mechanistic conception, at least as an ideal tendency, continued until almost the whole of the last century to constitute the premise generally accepted by science. The theoretical requirement and logical consequence of this conception were summarized in famous phrases by Laplace (Théorie analytique des probabilités, Paris 1820, pp. II-III).
The nineteenth century, however, also witnessed the rise of an antimechanistic current, grounded in positivism and energetics (v. DINAMISMO; ENERGIA). The positivists, Comte (v.) MARCHE (v.), level against mechanicism the same reproach that it had made against Aristotelianism in the seventeenth century, since it too resorts, in order to explain phenomena, to hypothetical occult entities, invisible particles and movements that would be the cause of visible phenomena. Positivist science, on the other hand, wishes to confine itself to sense data, in order to describe the concatenations and constants of phenomena, the laws of nature, without seeking a beyond, without resorting to metaphysical hypotheses; thermodynamics would provide an example of this. The influence exerted by this philosophy was considerable; and in minds which, while accepting its principles, felt the need for a concrete representation, it gave rise to a new epistemological theory midway between positivism and mechanicism: the theory of models, which enjoyed its greatest vogue in England with J. K. Maxwell (Memorie, published in the Philosophical magazine, 1861-62; Treatise on electricity and magnetism, London 1873), W. Thomson (Lectures on molecular dynamics and the wave-theory of light, Baltimore 1884; Popular lectures and addresses, London 1889-94), O. Lodge (Modern views on electricity, there 1889), and was also taken up in Germany with H. Hertz (Gesammelte Werke, Leipzig 1894-95) and in Italy with A. Garbasso and A. Pastore (Logica formale dedotta dalla considerazione dei modelli meccanici, Turin 1906). The theory of models retains the mechanistic explanation, going so far as to assert with Thomson that a phenomenon is rendered intelligible when a mechanical model of it has been constructed; yet it does not attribute to these models any real ontological value, but regards them as a purely mental, subjective schema.
At the beginning of the twentieth century, however, advances in chemistry and in kinetic molecular theory, and especially the experiments on emulsions conducted by J. Perrin (Les atomes, Paris 1914) for the determination of Avogadro’s number and molecular magnitudes, made an important contribution to the controversy between positivists and mechanists. Kinetic molecular hypotheses, although not becoming, in the strict sense, objects of experience, received such confirmation as to place beyond dispute the possibility of ontologically true mechanical representations. The impression upon physicists who were more or less positivist was enormous: the atom and its movements ceased to be convenient fictions and ideal entities and became real entities, a laboratory reality (cf. Bulletin de la soc. franç. de phil., sciences du 27 jan. et 3 mars, 10 [1910], pp. 81-121; H. Poincaré, Dernières pensées, Paris 1913, pp. 196-99; L. Brunschwig, L'expérience humaine et la causalité physique, there 1922, pp. 375-76). The mechanistic philosophical conception also benefited from this success; MEYERSON, EMILE (v.) became its principal exponent, and many physicists and philosophers identified it with kinetic molecular physical theory.
III. CRISIS OF MECHANICISM
Nevertheless, many of the observations already advanced by the energetists, and even more so the developments in physics over the last fifty years, have inevitably led physicists to revise the fundamental postulates of the scientific constructions from the seventeenth to the nineteenth century and perhaps definitively to renounce a general interpretation of a mechanical order. Impact, with the elastic forces awakened in it; the attractive and repulsive central forces; the electromagnetic forces depending jointly on charge, distance, and velocity, and acting perpendicularly to the line joining the centres; radiant energy; and gravitational and electromagnetic fields had already manifested themselves as phenomena irreconcilable with the fundamental position of mechanism, requiring the acceptance of real elements distinct from pure extension and local motion and thus necessarily introducing the Aristotelian notion of variable quality, as has already been observed with regard to impulse (cf. Hoenen, op. cit., pp. 149–60).More fundamental is the permanent theoretical crisis within the very essence of mechanism, which was brought to light by Meyerson himself. Mechanism, yielding to the demand for visualizing reality, limits rationality to identity and permanence; but a rationalization of the world understood in this sense inevitably leads, if one wishes to escape Eleatic monism, to the denial of rationality itself. Just as Democritus had resorted to affirming the reality of nothingness, so Meyerson too is compelled to admit
the existence of the irrational. There is something that resists rationalization as it is understood by mechanism: thought, sensation, energy; local motion itself presupposes forces acting to cause its variation and transmission from one body to another; even the simple numerical multiplicity of the one fundamental matter presupposes an inexplicable heterogeneity in the face of the demand of mechanistic rationality. Hence Meyerson’s conclusion, which is the logical conclusion of every mechanistic system: science arises from the clash between the rational and the irrational.
Finally, the theories of relativity and of quanta have brought new difficulties to the mechanistic interpretation, with the relativity of measurements of space and time, the variability of mass, the conversion of mass into energy, the quantization of elementary phenomena, the dualism between corpuscle and wave, the principle of indeterminacy, the new statistics of Fermi and Bose with the indistinguishability of corpuscles, etc. Indeed, the difficulties are such that many physicists believe they must conclude not only that a mechanistic representation is to be excluded, but that any objective representation of elementary realities must be excluded, returning to the positivistic conception of science. On the other hand, however, in describing reality physicists spontaneously make use of distinctly Aristotelian terminology, such as energetic and potential states; the distinction of the true atom as a unitary totality from the mere dynamic combination of electron and proton (line spectrum and continuous spectrum); the virtual presence of electrons and mesons in the nucleus; transformations of protons into neutrons and vice versa, not through the simple aggregation or disintegration of identical permanent elements; and the generation and destruction of pairs of electrons. All this suggests the possibility that science may attain an objective vision of the physical world and of its elements, but not a mechanistic one, and therefore one in agreement with Aristotelian-Thomistic epistemology and cosmology.