Paola Rumore (University of Turin/Univ. of Halle)


The paper focuses on the role of Kant’s refutation of materialism in his understanding of the Enlightenment, meant to be the necessary condition that allows human beings to express their proper dignity, i.e. to cultivate the urge for and the vocation of free thought. Sketching the main moments of the German struggle against the threat of materialism, the paper places Kant’s refutation within this tradition, and reconstructs the steps of his critique from the very beginning of his reflection – still dealing with the main topics of Wolff’s metaphysic – up to the definitive refutation he develops on the basis of the transcendental idealism of the first Critique. The shift from the «obscure reasons» pointed out in the Dreams, that allow a refutation of materialism on moral grounds, to the statement of the meaninglessness of the question in a transcendental perspective reveals that the attempt to find a solution to the problem of materialism – most of all in its psychological meaning –represents a never- ending challenge within Kant’s reflection.

Key words

Enlightenment, Refutation of Materialism, Psychological Materialism, Rational Psychology.


El artículo se centra en el papel que la refutación del materialismo de Kant desempeña en su comprensión de la Ilustración, habida cuenta de que se trata de la condición necesaria que permite que los seres humanos expresen su propia dignidad, esto es, que cultiven el deseo y la vocación al libre pensamiento. De la mano de la presentación de los momentos principales del combate alemán contra el materialismo, el artículo sitúa la refutación de Kant dentro de esta tradición y reconstruye los pasos de su crítica desde el comienzo de su reflexión –aún relacionada con las cuestiones principales de la metafísica de Wolff- hasta la refutación definitiva que desarrolla sobre la base del idealismo trascendental de la primera Crítica. El desplazamiento desde las “razones oscuras” señaladas en los Sueños, que permite basar una refutación del materialismo en fundamentos morales, hasta la afirmación de la falta de significado de la cuestión desde una perspectiva trascendental revela que el intento de encontrar una solución al problema del materialismo –sobre todo en su significado psicológico- representa un reto infinito dentro del pensamiento de Kant.

Palabras clave

Ilustración, refutación del materialismo, materialismo psicológico, psicología racional

  1. German Enlightenment and the threat of materialism

    It is well known that Kant concludes his essay on the Enlightenment with a sincere praise of the «age of Enlightenment» he was living in, the century of Frederick the Great, who had managed to achieve among his citizens the delicate balance between the private and the public use of reason. Kant presents this balance as the unavoidable condition that allows anybody to cultivate «the urge for and the vocation of free thought» (WA, AA 08: 41.34). In the ability to use one’s own understanding without another’s guidance, and to act freely in any field of reflection – in matters of arts, sciences, and, above all, in religious matters – Kant recognizes the seed that nature has carefully cultivated within the hard core of human beings, that is, their intrinsic value.

    Less well known is the fact that, in order to reinforce his conviction, Kant mentions the old, deplorable but in his view outdated opinion of those who reduce human beings to the deterministic realm of natural mechanical laws. «At last free thought – Kant states in the final sentence of his essay – acts even on the fundamentals of government, and the State finds it agreeable to treat man, who is now more than a machine, in accord with his dignity» (WA, AA 08: 41.35-42.2). Considering man as a mere machine – as Kant suggests in these lines – implies at least a misunderstanding, if not a denial, of human value and dignity.

    The appeal not to treat persons as ‘mere machines’ comes out again in a later letter written to Kant by a young physician, Carol Arnold Wilmans, then published by Kant himself in 1798 as an Appendix to the first part of his Conflict of the Faculties. The letter, which was enclosed with Wilmans’ dissertation on the similitude between pure mysticism and Kant’s doctrine of religion, deals with the central issue of critical philosophy, namely with the statement that man – as citizen of two worlds – finds himself between the reign of nature and that of freedom, connecting the two. «I have learned from the Critique of Pure Reason – so Wilmans

    – that philosophy is not a science of representations, concepts and Ideas, or a science of all the sciences, or anything else of this sort. It is rather a science of man, of his representations, thoughts and actions: it should present all the components of man, both as he is and as he should be – that is, in terms both of his natural functions and of his relations of morality and freedom» (SF, AA 07: 69.18-24)1. In order to strengthen his thesis, Wilmans recalls the false conception of those philosophers who «were quite mistaken in the role they assigned man in the world, since they considered him a machine within it, entirely dependent on the world or on external things and circumstances, and so made him an all but passive part of the world» (SF, AA 07: 69.24-70.1). In opposition to machines, which are determined from outside, by

    1 SF, AA 07: 69-70 (Appendix to the first part: On a Pure Mysticism in Religion).

    natural laws, «man should be determined solely by himself in so far as he has raised himself to his original dignity and independence from everything but the [moral] law» (SF, AA 07: 69.18-24). Here again the focus is on the two main topics, which Kant had already considered in opposition fifteen years earlier, in the passage we have just quoted, i.e. the image of the man-machine and the issue of human dignity. The persistence of such topics confirms once more that towards the end of the 18th century the modern and the early modern mechanical conception of man still surivived as a deep-rooted philosophical common view that – even if Kant means it to be outdated – still deserved refutation.

    The «man-machine» model in modern philosophy – in the version that dominates since, at least, Descartes' late work on the Passions of the soul – starts circulating in Germany with a suspect shadow and a notable force around the middle of the 18th century. While in the first decades of the century the image of the machine was broadly used with an almost neutral meaning to indicate human bodies2, the publication of La Mettrie’s L’homme machine and its claim to extend the machine-model to man in its entirety represents a turning point in the perception of such a figure referring to human beings. The anonymous writing appeared in 1748 – almost four decades before the publication of Kant’s pamphlet on the Enlightenment –

    , in the very same year its persecuted author got generously hosted at Frederick’s court in Berlin. Although Frederick never showed a high regard for La Mettrie’s philosophical views3, and even if his hospitality can be read – as Wilhelm Dilthey did (Dilthey 1901, pp. 116-117) – as an attempt to show to the entire world how in his Prussia the practice of tolerance was actually unlimited, it is undeniable that, after the early abandonment of the principles of Wolff’s metaphysics and the endorsement of the empirical and skeptically oriented view of the philosophes, Frederick’s opinion about the nature of man and his place in the world changed radically. Although he never came close to La Mettrie’s materialistic

    2 The figure of the body-machine was widespread in the Wolffian realm of German philosophy, without any dangerous significance. Cf., for instance, Wolff 1729, § 2, p. 341; Meier 1751, p. 3: «ich stelle mir demnach einen Gottesacker als eine Werckstat der Natur vor, wo sie die Ueberbleibsel der Menschen klüglich und sparsam zusammenstellt. Sie nimmt die Machine des menschlichen Körpers an diesem Orte aus einander, und braucht sie zu dem Baue tausend anderer Körper, welche sie auf der Schubühne dieses Erdbodens von neuem aufzustellen willens ist». Problems arise with the shift from the image of the body-machine to the man-machine,

    i.e. to the reduction of the man as a whole to the mechanical laws that rule the realm of matter. And with the consequent abandonment of the dualitic perspective in favor of a substance monism that excludes a proper space for the spiritual soul.

    1. Frederick to Wilhelmine, 21.11.1751 (Frederick 1846-56, XXVII a, 230): «Nous avons perdu le pauvre La Mettrie. Il est mort pour une plaisanterie, en mangeant tout un pâté de faisan; après avoir gagné une terrible indigestion, il s'est avisé de se faire saigner, pour prouver aux médecins allemands qu'on pouvait saigner dans une indigestion. Cela lui a mal réussi; il a pris une fièvre violente qui, dégénérée en fièvre putride, l'a emporté.a Il est regretté de tous ceux qui l'ont connu. Il était gai, bon diable, bon médecin, et très-mauvais auteur; mais, en ne lisant pas ses livres, il y avait moyen d'en être très-content». Cf. Zeller 1886, p. 30-31.

      position, or to Holbach’s even more radical claim, defending with Voltaire the faith in God against atheism and, finally (in the 70s), the freedom of will against the fatalism of the System of nature (1770)4, Frederick’s conception of man, and especially of the soul soon veered toward the sensualistic principles of the philosophes. In a letter to Voltaire, written in December 1775, he rejects firmly the dualistic idea of human nature: «I am pretty sure – so Frederick – that my nature is not twofold, and I conceive myself as a unitary being. I know, I am a material, animated, organized and thinking animal (un animal matériel, animé, organisé, et qui pense). I conclude therefore that animated matter can think as well as it has the property of being electric (la matière animéè peut penser, ainsi qu’elle a la propriété d’etre électrique)»5. According to the new understanding of animated matter, prevailing among the sensistic fringes of the Berlin Academy of Sciences – and even shared by La Mettrie – Frederick affirms in the same letter his intention to talk about the soul on the ground of experience, and to explain the phenomena of life and thinking by means of physical and mechanical principles: life and thought directly depend on the heat and on the movement of the main components of the animal body, that is, of nerves and blood. «I examine the soul from a medical, rather than from a metaphysical point of view», concludes Frederick – medicine only can provide a sufficient empirical and experimental certainty; metaphysics, on the contrary, leads rather to skeptical ignorance.

      The Francophile milieu of Frederick’s court was expressive of a naturalistic, mechanical conception of man which was not exceptional but rather widespread in 18th century Germany. The debate on materialism had been introduced in Germany already in the 20s by Heinrich Köhler’s translation of the correspondence between Leibniz and Samuel Clarke, where

      Leibniz hinted explicitly at Locke’s hypothesis of thinking matter as a theoretical justification of the materialistic claim6. The threat of materialism potentially implied by Locke’s hypothesis – and most of all of its epistemic ground, i.e. the impossibility of knowing the real essence of things – is one of the main topics discussed by Wolff and by the pietistic inclined

      theologian Johann Franz Budde in the context of the notorious struggle against Wolffianism

    2. Cf. Frederick to Voltaire, 3.12. 1736 (Frederick 1846-56, XXI, p. 23), 5.3.1749 (Frederick 1846-56, XI, p.

      155) and 4.12.1775 (Frederick 1846-56, XXIII, p. 404). On Frederick’s difficulties in order to conciliate this view with the defence of human freedom cf. Mori 2013, pp. 23-33.

    3. Frederick to Voltaire, 4.12.1775 (Frederick 1846-56, XXIII, p. 404).

    6 Cf. Köhler 1720; Wolff, who wrote the preface to Köhler’s translation (Wolff 1720), introduces the new philosophical category («Materialisten» / «Materialismus») in the preface to the second edition of his German Metaphysics in 1721. Instead of being a mere terminological innovation, Wolff’s explicit reference to this

    «philosophical sect» reveals that he sees in the materialistic account a precise ontological commitment (Wolff 1721, p. 18*-19*). On this topic, cf. Rumore 2013, p. 69-85.

    in the middle 20s7. About 20 years later, the theme resurfaced in the German debate thanks to Johann Gustav Reinbeck, again a Lutheran theologian, but unlike Budde a supporter of Wolff’s philosophy, who published the German translation of a famed anonymous writing

    about thinking matter – most likely a spurious version of Voltaire’s Letter on Locke – and its severe refutation according to the principles of the new rational psychology8. Reinbeck’s translation produced a broad debate about both the theoretical basis of materialism, an its actual dangerousness for the foundation of morals and for religious credo. Georg Friedrich

    Meier’s several and influential writings on the nature of the soul, its relation to the body, and its immortality are only the tip of an iceberg with a much broader base9. While the intense debate on the possibility of a rational argument against the materialistic refutation of the simplicity of the soul introduced by Meier came along, the publication of L’homme machine

    rose a harsh controversy which found its most resounding expressions in Albrecht von Haller’s campaign against La Mettrie on the «Göttingische gelehrte Anzeigen»10. In general, until that moment materialism represented in Germany a sort of spectrum against which one could react either condemning it, or trying to contain its dangerous potential. In the first half of the 18th century, German culture did not produce any endogenous relevant form of materialistic philosophy, but tended to import suggestions (as in the case of Locke) or concrete materialistic ideas (as in the case of the Epistula gallica or of La Mettrie’s writings)

    from abroad. Only in the 70s the materialistic approach seemed actually to find a proper German expression, as a small group of philosophers in Göttingen – first and foremost Michael Hißmann and Christoph Meiners – successfully attempted to introduce in Germany the physiological conception of man coming from the British scholarship of David Hartley

    and Joseph Priestley, and stressing specifically its materialistic implications11. Kant’s

    transcendental philosophy exercised its deep influence also on this debate, changing radically the perspective on the topic by calling into question first of all the legitimacy of a materialistic claim. Nevertheless, the attempt to introduce a metaphysical materialistic perspectives in philosophy continued to be emphasized even after Kant’s condemnation of

    7 Budde’s thesis of the impossibility to know the real essence of things makes it possible to conceive extension and thought as two properties belonging to the same being (in a sort of dogmatic radicalization of Locke’s epistemic claim): cf. Wolff 1724; Wolff 1724 a; Budde 1724; Walch 1724; on the topic, cf. Rumore 2013, p. 86- 101; Schröpfer 1980.

    8 The original title of the so-called Epistula gallica (French letter) was: Copie d’un Manuscript ou l’on soutient

    que c’est la matiére qui pense; cf. Reinbeck 1740.

    9 Meier 1743, 1746, 1748, 1751, 1752; cf. Rumore 2011, 2014.

    10 On this topic cf. Knabe 1978, pp. 121-48; but the reception of La Mettrie goes far beyon the affaire with Haller: an exaustive reconstruction of this topic is still a desideratum.

    11 On Hißmann, cf. Klemme et al. 2012, Wunderlich 2010, Rumore 2013, pp. 188-202; on the debate in Göttingen, Wunderlich 2012.

    such a claim12. But already during the so called pre-critical period, in the years of the elaboration of his critical philosophy, Kant could not avoid participating in the struggle against the threat of materialism, which was – as I have pointed out – one of the main items of the German philosophical agenda. The discussion on that topic engaged even Kant, who dealt with it from the very beginning of his philosophical career up to his late writings. Kant’s explicit hint to the still widespread imagine of the ‘man-machine’ in his essay on Enlightenment should therefore be understood as a further step along his uninterrupted confrontation with the philosophical view still debated in German culture almost at the end of the age of Enlightenment.

  2. Before the first «Critique»: Kant’ obscure reasons against materialism

    The problem of psychological materialism13, i.e. of the material nature of the soul, occupies Kant’s reflections from the very beginning of the 50s. The hypothesis of thinking matter was a central item for both Kant’s main authors, Alexander Gottlieb Baumgarten and Georg Friedrich Meier. The question as to whether upon an extended, and therefore composed, substance could be entrusted the capacity for thinking was considered a central issue by these

    authors, who elaborated their reflections within the realm of the Leibnitian metaphysical theory of monads. Baumgarten faced the problem in a central paragraph of his Metaphysica14, whereas Meier – besides dealing with it in his handbooks of logic and metaphysics – already in the 40s devoted at least two specific writings to the refutation of that metaphysical


    Kant’s early reflections on this issue are deeply influenced by the analysis of his authors, even if his investigation moves from a very different metaphysical premise, one rather oriented

    12 Cf., for instance, Knoblauch 1787; Rumore 2013, p. 202-208.

    13 As far as I see the distinction of different species of materialism goes back to Gerog Friedrich Meier: «A general Materialist (allgemeiner Materialist) believes that all substances, both finite and infinite, are composed beings, and considers it is absurd to admit simple substances or monads. Materialism can be theological, psychological and cosmological. The first one asserts that God, the infinite substance, is a composite being [...]. The second one asserts that finite spirits, especially human and animal souls, are composite beings [...]. The cosmological materialist asserts that there is no simple substance in the world, since every substance is a composite being. A general materialist is always even a cosmological materialist [...], but the contrary is not

    always true: one can admit that every [finite] substance in the world is composite, and that only God has a simple nature», Meier 1756, § 361.

    14 Baumgarten 1739, § 742: «Materia cogitans est in mundo impossibilis. Quicquid cogitare potest, aut est

    substantia, monas, aut totum, cuius substantia, quae cogitare potest, pars sit. Ergo omnis anima est substantia, monas. Quicquid intelligere potest, potest cogitare. Ergo quicquid intelligere potest, aut est substantia, monas, spiritua, aut tutum, cuius spiritus pars est».

    1. Cf. supra, footnote 14.

      towards a clear dualistic conception of substance. The New Elucidation of 1755 offers a good example of Kant’s early position on this topic. Explaining the two principles of metaphysical knowledge that derive from the principle of determining reason, Kant considers the concept of the «simple substance» as the basis of Wolff’s metaphysical psychology. According to Wolff, the simple substance has in itself the reason of its own modifications; hence, in his view, the latter develop independently from the relation with other external substances. What this means for the soul, is that the modifications produced by the vis repraesentativa have no causal relation with the modifications occurring in the body. On the contrary, in this early writing Kant rejects the hypothesis of the capacity of substance to cause its own internal changes by itself: he opposes to this conception the so called «principle of succession», according to which – as we read in the XII Proposition – «No change can happen to substances except in so far as they are connected with other substances; their reciprocal dependency on each other determines their reciprocal changes of state»16. According to this principle, the soul gains its representations in so far it is connected with a body: «if the human soul were free from real connections with external things – so Kant – the internal state of the soul would be completely devoid of changes» (PND, AA 01: 412). The statement of an indissoluble nexus between soul and body leads Kant to take precautionary measures against a possible charge of supporting the pernicious opinion of the materialists. Against this charge, he emphasizes the deep difference between the two substances: he does not deprive the soul of its representational state, even though he openly admits that the soul’s state would be immutable and constantly like itself if it were completely released from external connection (PND, AA 01: 412). The soul and the organic body maintain their different nature, even if they are strictly connected in performing their respective functions. The much discussed hypothesis of thinking matter is here definitively rejected: for philosophers as the «celebrated Crusius» who – in a Lockean way – admit the possibility that God, if he so willed, suspend the law according to which the soul’s striving to produce representation is always united with a striving of its substance to produce certain external motions, this would mean to admit «that the nature of the mind would have to be transcreated» (PND, AA 01: 412). According to Kant, both thinking in the soul and movements in bodies derive from the «universal action of spirits on bodies and of bodies on spirits» (PND, AA 01: 415), which he explains with a labored compromise between the harmonical view of the Leibnitians, Baumgarten’s ideal

    2. PND, AA 01: 410: «Nulla substantiis accidere potest mutatio, nisi quatenus cum aliis connexae sunt, quarum dependentia reciproca mutuam status mutationem determinat».

      influxionism and Martin Knutzen’s system of efficient causes. The second metaphysical principle mentioned in the New Elucidation (the principle of co-existence) affirms namely that «finite substances do not, in virtue of their existence alone, stand in a relationship with each other, nor are they linked together by any interaction at all, except in so far as the common principle of their existence, namely the divine understanding, maintains them in a state of harmony in their reciprocal relations» (PND, AA 01: 413).

      If the necessary relation between the substances assures the existence of the external world, avoiding the danger of idealism (which concerned even Wolff’s philosophy), yet, it is not that much efficacious against the threat of materialism, because the heterogeneity of spirit and matter depends here at last on the impossibility of considering the mind a sort of epiphenomenon of the organic body17. In this writing, Kant does not provide any explanation of the metaphysical difference of the two substances, but approaches the psychophysical problem in a rather naive way without calling metaphysical dualism into question.

      This approach persists almost steadily in Kant until the middle of the 60s, when two fortuitous events prompt him to deal again and more carefully with the question:the public refutation of Emanuel Swedenborg’s Arcana Coelestia (1749-56), and the reading of Mendelssohn’s Phädon (1767).

      In 1766, in the same year of the publication of the Dreams of a Spirit-seer, Kant justifies himself with Mendelssohn – who appeared to be deeply irritated by the irreverent tone of Kant’s writing – confessing his embarrassment in choosing the right way to deal with such a thorny theme without raising derision among the readers. The theme he is referring to is the possibility of rational psychology as a science, and especially the possibility of achieving a grounded knowledge of the nature of the soul, of its presence in the physical world, and of the phenomena of life and death, by means of mere reason, apart from any reference to experience18. In the dogmatic section of the Dreams, Kant shows how the concept of spirit is not an empirical, but rather a «surreptitious», concept, a «product of covert and obscure inferences made in the course of experience». «These concepts then – so Kant – proceed to propagate themselves by attaching themselves to other concepts, without there being any awareness of the experience itself on which they were originally based» (TG, AA 02: 321 note). Nevertheless, although these concepts are in most cases mere illusions of the imagination, they are not always erroneous (TG, AA 02: 321 note). Dealing with them, we are

    3. On the weakness of this antimaterialistic argument cf. Ameriks 2000, pp. 303-321. 18 Kant to Mendelssohn, 8.4.1766 (Br AA X: 69-73).

    compelled to derive the properties of the beings they refer to by contrast with their opposites provided by experience. In the case of the spirits, it means: by contrast with the properties of material beings in this way one concludes that, for what concerns their internal quality, spirits are beings bestowed with reason; and for what concerns the external qualities, that they are unextended, impenetrable, indivisible, and not subject to mechanical laws (TG, AA 02: 320- 21)19. But, since experience does not provide any positive support to the inferences of the imagination, those qualities are nothing but presupposed; so that Kant conclusion is that we can demonstrate neither the nature of spirits, nor their possibility itself.

    Besides refuting one of the stronghold of rational psychology, i.e., the claim of gaining the concept of a spirit in itself, Kant here also attacks another central argument of the Wolffian theory of the soul: the so-called simplicity argument presenting the item of the unity of consciousness, still considered the necessary condition of thought. Mendelssohn himself n Phädon constructed his own demonstration by arguing that if thinking requires a unitary substance, the soul must be simple, and therefore unextended, indivisible and so on (Mijuskovic 1974). «We find in the works of philosophers many good and reliable proofs that everything which thinks must be simple; and that every substance which thinks according to reason, must be a unit of nature; and that the indivisible Ego could not be divided among many connected things which make up a whole. My soul, therefore, must be a simple substance. But this proof leaves still undecided, whether the soul be of the nature of such things as, united in space, form an expanded and impenetrable whole; whether, therefore, it be material, or whether it be immaterial, and, consequently, a spirit; and, what is more, whether such beings as are called spirits, are possible» (TG, AA 02: 322).

    Kant here warns readers against the tendency to consider the possibility of what belongs to ordinary experience well understood, so that we come to consider impossible in itself what, on the contrary, falls out from our experience. It is precisely what happens in the case of the judgment that «matter offers a resistance in the space which it occupies». In fact we do recognize the impenetrability of matter by experience, but we don’t understand its possibility. Human understanding recognizes the existence of this force of resistance, but does not conceive its possibility. Nothing would prevent the possibility of conceiving different substances that possess forces which differ from the force of resistance whose effect is impenetrability. Those substances would occupy a space as well as matter, even if not by

    19 TG, AA 02: 319: «A spirit is a being endowed with reason».

    filling it, as matter does (by means of a force of repulsion), rather by being active in space with their proper force (TG, AA 02: 323). This means that we may accept the possibility of immaterial beings without any fear that we shall be refuted, however, there is no hope of our ever being able to establish their possibility by means of rational arguments (TG, AA 02: 323). That’s why Kant states that «my soul, in its manner of being present in space, would not differ from any element of matter, and since the power of understanding is an inner property which I cannot perceive in these elements of matter, even if that property were present in all of them, it follows that no valid reason can be adduced for supposing that my soul is not one of the substances which constitute matter, or for supposing that its particular manifestations should not originate exclusively from the place which it occupies in such an ingenious machine as the body of an animal, and in which the confluence of the nerves assures the inner capacity of thought and the power of will» (TG, AA 02: 326).

    To this almost accidental inclination towards a materialistic conception of the soul, Kant opposes a very weak objection: «I confess that I am very much inclined to assert the existence of immaterial natures in the world, and to put my soul itself into that class of beings*. * The reason of this, which appears to myself very obscure, and probably will remain so, concerns at the same time that which sensates in animals. Whatever in the world contains a principle of life, seems to be of immaterial nature» (Refl. 5458, AA 28.2: 188, between 1776 and 1778). The statement of a principle of life, i.e. of the capacity of everybody to determine themselves according their free will and their spontaneity, juxtaposes the realm of immaterial natures to the material world and its strict necessity.

    It being understood – and even recently remarked by scholars (Johnson 2002) – that these passages show Kant’s vague sympathy for the materialistic item (and, beside it, Kant’s deep dislike against any abstract speculation), the real sense of the whole discussion emerges however at the end of the writing, in the «Practical conclusion» that contains a brief and sharp treatise on the method of metaphysics, conceived as the «science of the limits of human reason» (TG, AA 02: 368). Given that it is impossible to achieve a grounded knowledge of the soul, neither by means of rational principles, nor by referring to experience, it is evident that the problem should be faced from another (non metaphysical) point of view. In doing so Kant shows the legacy of the empirical drift carried out by the second generation of Wolff scholars, in particular of the opportunity – already asserted by Meier – to solve in a pragmatic perspective those philosophical problems that go beyond the limits of human reason.

    Even the difference between learning and wisdom that Kant mentions in this Practical conclusion reflects the influence of Meier’s pragmatic approach. «To pursue every curiosity

    and to allow no limits to the thirst for knowledge apart from that of impotence – such zealousness does not ill-become learning. But, from among the innumerable tasks which spontaneously offer themselves, to choose that task, the solution of which is of importance to man – such choice is the merit of wisdom» (TG, AA 02: 369). A proper philosophical insight in the nature of the soul is impossible; but it belongs can be ascribed to the realm of those knowledges that are unuseful for our life and that we can therefore simply disregard (TG, AA 02: 372). It can be easily imagined that Mendelssohn – still engaged in the demonstration of the immortality of the soul by means of irrefutable rational arguments (Mendelssohn 1767) – become deeply irritated by this claim.

    As Meier had done before him, Kant also affirmed that our reason does not allow us to speak a definitive word on the materialistic hypothesis; where reason fails, the «heart of man» with its «immediate moral prescriptions» comes to help: as the thought that, with death, everything at the end cannot be bared at all by human soul, so «it seems more consonant with human nature and moral purity (Reiningkeit der Sitten) to base the expectation of a future world on the sentiments of a nobly constituted soul, than, conversely, to base its noble conduct on the hope of another world» (TG, AA 02: 373). Such is the character of the moral faith, whose simplicity on one hand sweeps away any philosophical sophistry, and on the other leads the man directly to his true purposes (TG, AA 02: 373).

    Kant’s approach seems to fit perfectly the statement of Max Dessoir, who noticed that German philosophy and psychology maintained all along the permanent inclination not to accept any (eventual) good reason for materialism: German philosophers «basically couldn’t come to a pact with the conformity [of human nature] to mechanical laws of the physical world, because in the most hidden wrinkles of their hearts they kept on hoping their souls were better than that» (Dessoir 1902, p. 210).

    Kant’s abandoning of the path of rational psychology does not imply his surrender against the hope for the immateriality of the soul and its immortality; rather, it must be understood as an attempt to invest his efforts in another human dimension, which he would elaborate more thoroughly in the years to follow, with the transcendental refutation of materialism developed in the Critique of pure reason.

  3. The first «Critique» and the transcendental refutation of materialism

The deep revolution raised on the philosophical scene by Kant’s first Critique also concerns the problem of psychological materialism,. Kant analyses it in a very peculiar way, absolutely

inconceivable within the former solutions provided by German philosophy. In the Kantian chapter of his History of materialism (1873-75), Friedrich Albert Lange acknowledged this radical gap in the history of philosophy: the Critique of pure reason represents, according to him, a real break between two eras. Moreover, this was the view Kant himself had about it: the gap between phenomena and noumena, and the tight dependency of phenomena on the transcendental activity of the subject «strike a blow at the root of materialism, fatalism, atheism, free-thinking, fanaticism, and superstition, which are universally injurious» (KrV B XXXIV). A long and substantiate tradition in the history of philosophy – that leads up to Alois Riehl – claims that this path was originally prepared by Locke and Berkeley, namely by their phenomenistic assumption, according to which our knowledge never reaches the things in their real essence, but remains within the field of our ideas (Riehl 1924). Less well-known is the fact that the idea of a divide (Scheidewand) between our senses and external things – a divide that hinders us in seeing things as they actually are – comes to Kant via Meier in the form of a «prejudice of empirical knowledge» (Meier 1766, § 29. Rumore 2005, XXXV- XXXVI; Hinske p.156-171). According to Lange, given that Kant’s reduction of experience to phenomena allows a clear defeat of materialism from a metaphysical point of view, it is remarkable that after Kant materialism is sort of resurrected in the epistemological field as the proper methodological item of natural sciences. And it is precisely on this spot that, in Lange’s view, Kant’s long-lasting credit in the history of materialism must be seen (Lange 1866, II.2).

Even if Lange’s analysis shows evident traces of the atmosphere of the return to Kant in a preeminently epistemic perspective, it is undeniable that after Kant materialism loses its metaphysical consistence. Kant’s transcendental idealism delegitimizes any further debate on the very nature of material substances and on their independence from mental activity. In the note to the Amphiboly of Concepts of Reflections, Kant states very clearly that «Matter is substantia fenomenon» and that any conjecture about its inward nature is nothing but «a phantom (Grille); for matter is not among the objects of pure understanding, and the transcendental object which may be the ground of this appearance that we call matter is a mere something of which we should not understand what it is» (KrV A 277 / B 333). The concept of matter, with its property of extension and impenetrability, does not exceed the boundaries of phenomena; at most, it can be seen as a regulative principle («supreme empirical principle of the unit of appearances»),,as Kant does when dealing with the cosmological proof of God’s existence (KrV A 618 / B 646).

In the first Critique, the refutation of cosmological materialism appears quite hasty. Not so for what concerns psychological materialism, to which Kant devotes – at least in the edition of 1781 – a much more accurate analysis. It is well-known that the first formulation of the chapter on the Paralogisms of pure reason differs radically from the B edition; the A edition can be read as an attempt to demonstrate the inconsistency of materialism, in general, and of every claim to make assertions on the properties of the subject of thought in comparison to those of matter, in particular. The question concerning the homogeneity or heterogeneity of mind and matter cannot be answered: given that matter is nothing but substantia phenomenon, there is no way to know if its noumenic constitution really differs from the one of the mind (KrV A 358-60).

«Matter, therefore, does not mean a kind of substance quite distinct and heterogeneous from the object of inner sense (the soul), but only the distinctive nature of those appearance of objects – in themselves unknown to us – the representations of which we call outer as compares with those which we count as belonging to inner sense, although like all other thoughts these outer representations belong only to the thinking subject» (KrV A 385).

In 1781 Kant condemns rational psychology on the ground that it cannot be used to extend knowledge, although he still insists on its «considerable negative value», if it is meant as nothing more than a critical analysis of the dialectical inferences that arise from our reason. Among those, our item plays a preeminent role:

«Why do we have resort to a doctrine of the soul founded exclusively on pure principles of reason? Beyond all doubt, chiefly in order to secure our thinking self against the danger of materialism». Transcendental idealism does not give any further knowledge of the properties of the thinking self, but it is nevertheless possible that we find cause, on other than mere speculative grounds, to hope for an independent and continuing existence of the thinking nature, throughout all possible changes of our state (KrV A 383). The (negative) utility of rational psychology is stated clearly in the B edition of the Paralogisms chapter, where Kant writes that this one «exists not as a doctrine [...] but only as a discipline» that keeps us from

«throwing ourselves into the arms of a soulless materialism» (KrV A 382-83; cf. KrV B 421). Given the impossibility of rational psychology as a science, the real danger of materialism concerns now the risk to «confine reason in practical respects» (Prol AA 04: 363). From Kant’s point of view it does not mean – as it did for Wolff, Mendelssohn and in some respect for Meier – that materialism detracts the grounds of morals and religion; on the very contrary,

it denies «the right of reason’s need, as a subjective ground for presupposing and assuming something which reason may not presume to know through objective grounds; and consequently for orienting itself in thinking, solely through reason’s own need, in that immeasurable space of the supersensible, which for us is filled with dark night» (WDO AA 08: 137).

The need of reason becomes in this way the very instrument of Kant’s refutation of materialism. Even in the late writing on Religion he comes back to this point: materialism, whether psychological or cosmological is «indeed, very well suited to man’s mode of sensuous representation, but most burdensome to reason in its faith regarding the future» (RGV AA 06: 128 note).

The definitive refutation of materialism is played out on the field of practical reason and of its undeniable need, which makes the hypothesis of the spirituality of rational world-beings

«more congenial to reason, not only because of the impossibility of making comprehensible a matter which thinks, but especially because of the contingency to which materialism exposes our existence after death by claiming that such existence depends solely upon the cohering of a certain lump of matter in a certain form, and denying the possibility of thinking that a simple substance can persist based upon its [own] nature» (RGV AA 06: 128 note).

Through pure rational faith Kant manages to provide a transcendental ground to the obscure conviction that lead him in the Dreams, i.e. to the statement that in the «scale of understanding», the arm which bears the inscription «Hope for the future» has a clear advantage on the one of speculation (TG AA 02: 349-50). Materialism – and its conception of man-machine –finally threatens the peculiar nature of human beings, its inward value and dignity that, according to Kant, can find its proper expression only in an age of Enlightenment. That’s why Frederick, «the man who is himself enlightened, who is not afraid of shadows» should better correct his position regarding this capital philosophical question.


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