Kant and the Self-Critique of the Modern Mind

Richard Tarnas

The intellectual challenge that faced Immanuel Kant in the second half of the eighteenth century was a seemingly impossible one: on the one hand, to reconcile the claims of science to certain and genuine knowledge of the world with the claim of philosophy that experience could never give rise to such knowledge; on the other hand, to reconcile the claim of religion that man was morally free with the claim of science that nature was entirely determined by necessary laws. With these several claims in such intricate and pointed conflict, an intellectual crisis of profound complexity had emerged. Kant’s proposed resolution of that crisis was equally complex, brilliant, and weighty in its consequences.

Kant was too intimate with Newtonian science and its triumphs to doubt that man had access to certain knowledge. Yet he felt as well the force of Hume’s relentless analysis of the human mind. He too had come to distrust the absolute pronounce­ments on the nature of the world for which a purely rational speculative metaphysics had been pretending competence, and concerning which it had fallen into endless and seemingly irresolvable conflict. According to Kant, the reading of Hume’s work had awakened him from his “dogmatic slumber,” the residue of his long training in the dominant German rationalist school of Wolff, Leibniz’s academic systematizer. He now recognized that man could know only the phenomenal, and that any metaphysical conclusions concerning the nature of the universe that went beyond his experience were unfounded. Such propositions of the pure reason, Kant demonstrated, could as readily be opposed as supported by logical argument. Whenever the mind attempted to ascertain the existence of things beyond sensory experience–such as God, the immortality of the soul, or the infinity of the universe–it inevitably found itself entangled in contradiction or illusion. The history of metaphysics was thus a record of contention and confusion, entirely devoid of cumulative progress. The mind required empirical evidence before it could be capable of knowledge, but God, immortality, and other such metaphysical matters could never become phenomena; they were not empirical. Metaphysics, therefore, was beyond the powers of human reason.

But Hume’s dissolution of causality also appeared to undercut the claims of natural science to necessary general truths about the world, since Newtonian science was based on the assumed reality of the now uncertified causal principle. If all human knowledge necessarily came from observation of particular instances, these could never be legiti­mately generalized into certain laws, since only discrete events were perceived, never their causal connection. Nevertheless, Kant was convinced beyond doubt that Newton, with the aid of experiments, had gotten hold of real knowledge of absolute certainty and generality. Who was correct, Hume or Newton? If Newton had attained certain knowledge, and yet Hume had demonstrated the impossibility of such knowledge, how could Newton have succeeded? How was certain knowledge possible in a phenomenal universe? This was the burden of Kant’s Critique of Pure Reason, and his solution was to satisfy the claims of both Hume and Newton, of skepticism and science–and in so doing to resolve modern epistemology’s fundamental dichotomy between empiricism and rationalism.

The clarity and strict necessity of mathematical truths had long provided the rationalists–above all Descartes, Spinoza, and Leibniz–with the assurance that, in the world of modern doubt, the human mind had at least one solid basis for attaining certain knowledge. Kant himself had long been convinced that natural science was scientific to the precise extent that it approximated to the ideal of mathematics. Indeed, on the basis of such a conviction, Kant himself had made an important contribution to Newtonian cosmology, demonstrating that through strictly necessary measurable physical forces, the Sun and planets had consoli­dated and assumed the motions defined by Copernicus and Kepler. To be sure, in attempting to extend the mathematical mode of reasoning to metaphysics, Kant became convinced of pure reason’s incompetence in such matters. But within the bounds of sensory experience, as in natural science, mathematical truth was patently successful.

Yet because natural science was concerned with the external world given through the senses, it thereby opened itself to Hume’s criticism that all its knowledge would then be contingent, its apparent necessity only psychological. By Hume’s reasoning, with which Kant had to agree, the certain laws of Euclidean geometry could not have been derived from empirical observation. Yet Newtonian science was explicitly based upon Euclidean geometry. If the laws of mathematics and logic were said to come from within the human mind, how could they be said to pertain with certainty to the world? Rationalists like Descartes had more or less simply assumed a mind-world correspondence, but Hume had subjected that assumption to a damaging critique. Nevertheless, a mind-world correspondence was clearly presupposed, and seemingly vindicated, in the Newtonian achievement, of which Kant was certain.

Kant’s extraordinary solution was to propose that the mind-world correspondence was indeed vindicated in natural science, yet not in the naive sense previously assumed, but in the critical sense that the “world” science explicated was a world already ordered by the mind’s own cognitive apparatus. For in Kant’s view, the nature of the human mind is such that it does not passively receive sense data. Rather, it actively digests and structures them, and man therefore knows objective reality precisely to the extent that that reality conforms to the fundamental structures of the mind. The world addressed by science corre­sponds to principles in the mind because the only world available to the mind is already organized in accordance with the mind’s own processes. All human cognition of the world is channeled through the human mind’s categories. The necessity and certainty of scientific knowledge derive from the mind, and are embedded in the mind’s perception and understand­ing of the world. They do not derive from nature independent of the mind, which in fact can never be known in itself. What man knows is a world permeated by his knowledge, and causality and the necessary laws of science are built into the framework of his cognition. Observations alone do not give man certain laws; rather, those laws reflect the laws of man’s mental organization. In the act of human cognition, the mind does not conform to things; rather, things conform to the mind.

How did Kant arrive at this epoch-making conclusion? He began by noting that if all content that could be derived from experience was withdrawn from mathematical judgments, the ideas of space and time still remained. From this he inferred that any event experienced by the senses is located automati­cally in a framework of spatial and temporal rela­tions. Space and time are “a priori forms of human sensibility”: they condition whatever is apprehended through the senses. Mathematics could accurately describe the empirical world because mathematical principles necessarily involve a context of space and time, and space and time lay at the basis of all sensory experience: they condition and structure any empirical observation. Space and time are thus not drawn from experience but are presupposed in experience. They are never observed as such, but they constitute that context within which all events are observed. They cannot be known to exist in nature independently of the mind, but the world cannot be known by the mind without them.

Space and time therefore cannot be said to be characteristic of the world in itself, for they are contributed in the act of human observation. They are grounded epistemologically in the nature of the mind, not ontologically in the nature of things. Because mathematical propositions are based on direct intuitions of spatial relations, they are “a priori”–constructed by the mind and not derived from experience–and yet they are also valid for experience, which will by necessity conform to the a priori form of space. It is true that pure reason inevitably becomes entangled in contradiction if it attempts to apply these ideas to the world as a whole–to ascertain what is true beyond all possible experience–as in trying to decide whether the universe is infinite or finite either in time or space. But as regards the phenomenal world that man does experience, time and space are not just applicable concepts, they are intrinsic components of all human experience of that world, frames of reference mandatory for human cognition.

Moreover, further analysis reveals that the character and structure of the mind are such that the events it perceives in space and time are subject to other a priori principles–namely, the categories of the understanding, such as the law of causation. These categories in turn lend their necessity to scientific knowledge. Whether all events are causally related in the world outside the mind cannot be ascertained, but because the world that man experiences is necessarily determined by his mind’s predispositions, it can be said with certainty that events in the phenomenal world are causally related, and science can so proceed. The mind does not derive cause and effect from observations, but already experiences its observations in a context in which cause and effect are presupposed realities: causality in human cognition is not derived from experience but is brought to experience.

As with cause and effect, so too with other categories of the understanding such as substance, quantity, and relation. Without such fundamental frames of reference, such a priori interpretive principles, the human mind would be incapable of comprehending its world. Human experience would be an impossible chaos, an utterly formless and miscel­laneous manifold, except that the human sensibility and understand­ing by their very nature transfigure that manifold into a unified perception, place it in a framework of time and space, and subject it to the ordering principles of causality, substance, and the other categories. Experience is a construction of the mind imposed on sensation.

The a priori forms and categories serve as absolute conditions of experience. They are not read out of experience, but read into it. They are a priori, yet empirically applicable–and applicable only empiri­cally, not metaphysically. For the only world that man knows is the empirical world of phenomena, of “appearances,” and that world exists only to the extent that man participates in its construction. We can know things only relative to ourselves. Knowledge is restricted to the sensible effects of things on us, and these appearances or phenomena are, as it were, predigested. Contrary to the usual assumption, the mind never experiences what is “out there” apart from the mind in some clear, undistorted mirroring of objective “reality.” Rather, “reality” for man is necessarily one of his own making, and the world in itself must remain something one can only think about, never know.

The order man perceives in his world is thus an order grounded not in that world but in his mind: the mind, as it were, forces the world to obey its own organization. All sensory experience has been channeled through the filter of human a priori structures. Man can attain certain knowledge of the world, not because he has the power to penetrate to and grasp the world in itself, but because the world he perceives and understands is a world already saturated with the principles of his own mental organization. This organization is what is absolute, not that of the world in itself, which ultimately remains beyond human cognition. But because man’s mental organization is absolute, Kant assumed, man can know with genuine certainty–know, that is, the only world he can experience, the phenomenal world.

Thus man does not receive all his knowledge from experience, but his knowledge in a sense already introduces itself into his experience in the process of cognition. Although Kant criticized Leibniz and the rationalists for believing that reason alone without sense experience can calculate the universe (for, Kant argued, knowledge requires acquaintance with particulars), he also criticized Locke and the empiricists for believing that sense impressions alone, without a priori concepts of the understanding, could ever lead to knowledge (for particulars are meaning­less without general concepts by which they are interpreted). Locke was correct to deny innate ideas in the sense of mental representations of physical reality, but wrong to deny innate formal knowledge. As thought without sensation is empty, so is sensation without thought blind. Only in conjunction can understanding and sensibility supply objectively valid knowledge of things.

For Kant, Hume’s division of propositions into those based on pure intellect (which are necessary but tautological) and those based on pure sensation (which are factual but not necessary) required a third and more important category, one involving the intimately combined operation of both faculties. Without such a combination, certain knowledge would be impossible. One cannot know something about the world simply by think­ing; nor can one do so simply by sensing, or even by sensing and then thinking about the sensations. The two modes must be interpenetrating and simultaneous.

Hume’s analysis had demonstrated that the human mind could never attain certain knowledge of the world, for the apparent order of all past exper­ience could not guarantee the order of any future experience. Cause was not directly perceivable in the world, and the mind could not penetrate beyond the veil of phenomenal experience of discrete particulars. It was therefore clear to Kant that if we received all our knowledge of things from sensation alone, there would be no certainty. But Kant then moved beyond Hume because he recognized the extent to which the history of science had progressed only on the basis of conceptual predispositions that were not derived from experience, but were already woven into the fabric of the scientific observation. He knew that Newton’s and Galileo’s theories could not have been derived simply from observations, for purely acciden­tal observations that have not been prearranged according to human design and hypothesis could never lead to a general law. Man can elicit from nature universal laws not by waiting on nature like a pupil for answers, but only, like an appointed judge, by putting shrewd questions to nature that will be deliberately and precisely revealing. Science’s answers derive from the same source as its questions. On the one hand, the scientist requires experiments to ascertain that his hypotheses are valid and thus true laws of nature; only by tests can he be sure there are no exceptions and that his concepts are genuine concepts of the understand­ing and not only imaginary. On the other hand, the scientist also requires a priori hypotheses even to approach the world, to observe and test it fruitfully. And the situation of science in turn reflects the nature of all human experience. The mind can know with certainty only that which it has in some sense already put into its experience.

Man’s knowledge, then, does not conform to objects, but objects conform to man’s knowledge. Certain knowledge is possible in a phenomenal universe because the human mind bestows to that universe its own absolute order. Thus Kant proclaimed what has been called his “Copernican revolution”: as Copernicus had explained the perceived movement of the heavens by the actual movement of the observer, so Kant explained the perceived order of the world by the actual order of the observer.1

By confronting the seemingly irresolvable dialectic between Humean skepticism and Newtonian science, Kant demonstrated that human observations of the world were never neutral, never free of priorly imposed conceptual judgments. The Baconian ideal of an empiricism totally free of “anticipations” was an impossibility. It could not work in science, nor was it even experien­tially possible, for no empirical observation and no human experience was pure, neutral, without unconscious assumptions or a priori orderings. In terms of scientific knowledge, the world could not be said to exist complete in itself with intelligible forms that man could empirically reveal if only he would clear his mind of preconcep­tions and improve his senses by experiment. Rather, the world that man perceived and judged was formed in the very act of his perception and judgment. Mind was not passive but creative, actively structuring. Physical particulars could not simply be identi­fied and then correlated by means of conceptual categories. Rather, the particulars required prior categorization of some kind to be identified at all. To make knowledge possible, the mind necessarily imposed its own cognitive nature on the data of experience, and thus man’s knowledge was not a description of external reality as such, but was to a crucial extent the product of the subject’s cognitive apparatus. The laws of natural processes were the product of the observer’s internal organiza­tion in interaction with external events that could never be known in themselves. Hence neither pure empiricism (without a priori structures) nor pure rationalism (without sensory evidence) constituted a viable epistemo­logical strategy.

The task of the philosopher was therefore radically redefined. His goal could no longer be that of determining a metaphysical world conception in the traditional sense, but should instead be that of analyzing the nature and limits of human reason. For although reason could not decide a priori on matters transcending experience, it could determine what cognitive factors are intrinsic to all human experience and inform all experience with its order. Thus philosophy’s true task was to investigate the formal structure of the mind, for only there would it find the true origin and foundation for certain knowledge of the world.

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The epistemological consequences of Kant’s Copernican revolu­tion were not without disturbing features. Kant had rejoined the knower to the known, but not the knower to any objective reality, to the object in itself. Knower and known were united, as it were, in a solipsistic prison. Man knows, as indeed Aquinas and Aristotle had said, because he judges things through the medium of a priori principles; but man cannot know whether these internal principles possess any ultimate relevance to the real world, or to any absolute truth or being outside the human mind. There was now no divine warrant for the mind’s cognitive categories, such as Aquinas’s lumen intellectus agentis, the light of the active intellect. Man could not determine whether his knowledge had some fundamental relation to a universal reality or whether it was merely a human reality. Only the subjective necessity of such knowledge was certain. For the modern mind, the inevitable outcome of a critical rationalism and a critical empiricism was a Kantian subjectivism limited to the phenomenal world: Man had no necessary insight into the transcen­dent, nor into the world as such. Man could know things only as they appeared to him, not as they were in themselves. In retrospect, the long-term consequences of both the Copernican and the Kantian revolutions were fundamentally ambiguous, at once liberating and diminish­ing. Both revolu­tions awakened man to a new, more adventurous reality, yet both also radically displaced man–one from the center of the cosmos, the other from genuine cognition of that cosmos. Cosmological alienation was thereby compounded by episte­mological alienation.

It could be said that in one sense Kant reversed the Copernican revolution, since he placed man again at the center of his universe by virtue of the human mind’s central role in establishing the world order. But man’s claim to be the center of his cognitive universe was only the obverse of his recognition that he could no longer assume any direct contact between the human mind and the universe’s intrinsic order. Kant “humanized” science, but in so doing, he removed science from any certain foundation independent of the human mind such as Cartesian and Baconian science–the original programs of modern science–had earlier enjoyed, or presumed. Despite the attempt to ground knowledge in a new absolute–the human mind–and despite, from one point of view, the ennobling status of the mind’s being the new epistemological center, it was also evident that human knowledge was subjectively constructed and therefore–relative to the intellectual certainties of other eras, and relative to the world in itself–fundamentally dislocated. Man was again at the center of his universe, but this was now only his universe, not the universe.

Yet Kant saw this as a necessary recognition of the limits of human reason, a recognition that would paradoxically open up a larger truth to man. For Kant’s revolution had two sides to it, one focused on science, the other on religion: he wished to rescue both certain knowledge and moral freedom, both his belief in Newton and his belief in God. On the one hand, by demonstrating the necessity of the mind’s a priori forms and categories, Kant sought to confirm the validity of science. On the other hand, by demonstrating that man can know only phenomena, not things in themselves, he sought to make room for the truths of religious belief and moral doctrine.

In Kant’s view, the attempt by philosophers and theologians to rationalize religion, to give the tenets of faith a foundation by pure reason, had succeeded only in producing a scandal of conflict, casuistry, and skepticism. Kant’s restriction of reason’s authority to the phenome­nal world thereby freed religion of reason’s clumsy intrusion. Moreover, by such a restriction, science would no longer conflict with religion. Since the causal determinism of science’s mechanistic world picture would deny the soul’s freedom of will, yet such freedom must be presupposed in any genuine moral activity, Kant argued that his limitation of science’s com­petence to the phenomenal, his recognition of man’s ignorance concern­ing things in themselves, opened up the possibility of faith. Science could claim certain knowledge of appearances, but it could no longer arrogantly claim knowledge over all of reality, and precisely this allowed Kant to reconcile scientific determinism with religious belief and morality. For science could not legitimately rule out the possibil­ity that the truths of religion were valid as well.

Kant thus held that although one could not know that God exists, one must nevertheless believe he exists in order to act morally. Belief in God is therefore justified, morally and practically, even if it is not certifiable. It is a matter of faith rather than knowledge. Ideas of God, the soul’s immortality, and the freedom of the will could not be known to be true in the same way that the laws of nature established by Newton were so known. Yet one could not justify doing one’s duty if there were no God, or if free will did not exist, or if one’s soul perished at death. These ideas must there­fore be believed as true. They are necessary to postulate for a moral existence. With the advances of scientific and philosophical knowledge, the modern mind could no longer base religion on a cosmologi­cal or metaphysical foundation, but instead it could base religion in the structure of the human situation itself–and it was through this decisive insight that Kant, following the spirit of Rousseau and of Luther before him, defined the direction of modern religious thought. Man was freed from the external and objective to form his religious response to life. Inner personal experience, not objective demonstration or dogmatic belief, was the true ground of religious meaning.

In Kant’s terms, man could view himself under two different, even contradictory aspects–scientifically, as a “phenomenon,” subject to the laws of nature; and morally, as a thing-in-itself, a “noumenon,” which could be thought of (not known) as free, immortal, and subject to God. Here the Humean and Newtonian influences in Kant’s philosophical development were countered by the universal humanitarian moral ideals of Rousseau, who had stressed the priority of feeling over reason in religious experience, and whose works had made a considerable impression on Kant, reinforcing the deeper roots of Kant’s sense of moral duty coming from his strict Pietist childhood. The inner experience of duty, the impulse to selfless moral virtue, permitted Kant to transcend the otherwise daunting limitations of the modern mind’s world picture, which had reduced the knowable world to one of appearance and mechanistic necessity. Kant was thereby able to rescue religion from scientific determinism, just as he had rescued science from radical skepticism.

But he rescued these only at the price of their disjunction, and of the restriction of human knowledge to phenomena and subjective certainties. It is clear that at heart, Kant believed that the laws moving the planets and stars ultimately stood in some fundamental harmonious relation to the moral imperatives he experienced within himself: “Two things fill the heart with ever new and always increasing awe and admiration: the starry heavens above me and the moral law within me.” But Kant also knew he could not prove that relation, and in his delimitation of human knowledge to appearances, the Cartesian schism between the human mind and the material cosmos continued in a new and deepened form.

In the subsequent course of Western thought, it was to be Kant’s fate that, as regards both religion and science, the power of his epistemological critique tended to outweigh his positive affirmations. On the one hand, the room he made for religious belief began to resemble a vacuum, since religious faith had now lost any external support from either the empirical world or pure reason, and increasingly seemed to lack internal plausibility and appropriateness for secular modern man’s psychological character. On the other hand, the certainty of scien­tific knowledge, already unsupported by any external mind-independent necessity after Hume and Kant, became unsupported as well by any internal cognitive necessity with the dramatic contro­version by twentieth-century physics of the Newtonian and Euclidean categories which Kant had assumed were absolute.

Kant’s penetrating critique had effectively pulled the rug out from under the human mind’s pretensions to certain knowledge of things in themselves, eliminating in principle any human cognition of the ground of the world. Subsequent developments in the Western mind–the deepening relativisms introduced not only by Einstein, Bohr, and Heisenberg, but also by Darwin, Marx, and Freud; by Nietzsche, Dilthey, Weber, Heidegger, and Wittgenstein; by Saussure, Levi-Strauss, and Foucault; by Godel, Popper, Quine, Kuhn, and a host of others–radically magnified that effect, altogether eliminating the grounds for subjective certainty still felt by Kant. All human experience was indeed structured by largely unconscious principles, but those principles were not absolute and timeless. Rather, they varied fundamentally in different eras, different cultures, different classes, different languages, different persons, different existential contexts. In the wake of Kant’s Coper­nican revolu­tion, science, religion, and philosophy all had to find their own bases for affirmation, for none could claim a priori access to the universe’s intrinsic nature.

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Richard Tarnas is Professor Emeritus at California Institute of Integral Studies. His books include Cosmos and Psyche and The Passion of the Western Mind (Random House, 1991) from which this article is excerpted (pp. 341-351)