There is perhaps no more influential epistemology on post Enlightenment philosophy than Kant, certainly there is at the very least no more influential modern philosopher. While the critical philosophy of Kant undoubtedly affected almost every discipline within philosophy, perhaps none were as radically altered by his critiques than the discipline of epistemology (although, as Fr. Schenk reminds us, where we jump in may not turn out as important as how we decide to proceed). Nevertheless, in arguing for a Copernican revolution in philosophy, Kant, to his mind, attempted to synthesize the empiricists and rationalists. Whereas the empiricists attempted to begin epistemological inquiry through an objective knowledge of an external world, Kant believed that it was the subject itself that imposes on the external world certain categories and knowledge. To be sure, one could make a reasonable argument that Kant was merely bringing Cartesian dualism to its logical conclusion. Where Descartes understood the relationship between the res cogitans and the res extensa as possible through interactionism in the pineal gland, Kant understood such an interaction was impossible. In this way Kant brought the Cartesian compromise to its skeptical completion, exposing the logical error Descartes was never able to fully appreciate, namely that no matter where such an interactionism is located the subject can never be fully able to know the res extensa as it really exists. The res cogitans could never penetrate the res extensa. The correspondence between knower and thing known was crushed under the weight of the knower’s subjectivity, and along with it all of metaphysics.
Most fundamental to Kantian epistemology is the distinction between analytic judgments and synthetic judgments. Analytical judgments are based on the law of non-contradiction, knowledge intuitively known through immediate inference. Specifically, such knowledge is a tautology, the information gleaned from analyzing the terminology. Moreover, such knowledge is a priori, that is, knowledge which is independent upon experience. On the other hand, synthetic judgments provide us with new knowledge of the world and rely on the ability to synthesize the subject with the predicate. In this manner, synthetic judgments form the bedrock of reason, forming the ability to rationally progress through logical statements. Moreover, synthetic judgments, according to Kant, are both a priori and a posteriori. As a priori judgments, synthetic knowledge is obtained independent from external experience of the subject. Juxtaposed with this, a posteriori judgments are gleaned from interaction with the external world of sensation. In a priori judgments, the more controversial distinction, Kant argues that there are judgments which give us knowledge of the world, but through a priori means. This might sound counter-intuitive, but for Kant it is a vital distinction for his understanding of mathematical judgments and judgments about phenomena which can never be universalized by pure observation. For example, ‘all events have a cause’ is not empirically based, we can never verify it through direct observation, yet we bring it to our presuppositions of the external world.
Another vital Kantian move in epistemology is the distinction between the phenomena and noumena. As mentioned above, the Copernican revolution for Kant requires that the human subject be understood as the beginning point for knowledge. We can never escape our limitations, positions, and subjectivity to stand outside ourselves and judge our interaction between self and external world. Hence, for Kant the ‘I think’ is the subjective condition for knowledge, which by definition can never be an objective condition. In this regard, Kant rejects both the empiricist and rationalist positions. Rationalists tend to believe there is a world which exists as a limited whole, a space/time condition in which the self exists. Empiricists tend to believe the world is unlimited, externally verifiable through proper observation. By rejecting both positions, Kant’s Copernican turn supplants both positions by arguing that the world is not an object ‘out there.’ Rather, our subjective condition allows for knowledge to come to the knower, but in a confused fashion, ultimately determined by categorization by the mind. Hence, Kant determines that there is a division between that which exists in its reality, the noumena, and that which comes to us in our subjective condition, determined by the mind’s categories, namely the phenomena.
Moreover, for Kant, the only manner in which the subjective self can have knowledge of the external world is through the phenomenon, never the noumena. However, Kant does not want to collapse into a complete solipsism in which the external world is in complete chaos, relative and lacking reality. Even though the cognitive subject can never know the extended world as it really exists, the appearance of that reality as the phenomenon is in some manner caused by the noumena. For Kant this is possible because causation is not an empirically verifiable principle based on direct observation, but rather a category used by the mind in order to structure the phenomena. However, this leaves room for problems in understanding the actual relationship between the noumena and phenomena. If in fact causation is mere mental construction, not a reality-in-and-of-itself, then how can we say with certainty that there is an actual causal relationship between the noumena and the phenomena? Perhaps there is no connection between the two, in which seemingly, Kantian epistemology does indeed slip into solipsism.
We must ask the question, under this epistemological model, what can we know? Seemingly, for Kant, the only knowledge available to the subject is the phenomenon. While he retains his position of the two stems of knowledge, empiricism and rationalism, both seem muted by the distinction between appearance and reality. If the phenomena are mere constructive structures determined by the mind, then reality, and knowledge of it, will always be elusive. Under such a model, only the appearance of such reality can be readily accepted into our noetical structure. But, perhaps more interesting, especially when held to the light of the history of philosophy, is Kant’s rejection of metaphysical knowledge, a clear result of the above distinction. The best metaphysics can achieve under such a narrow epistemological justification are transcendent illusions. Mirroring the noumena and phenomena distinction, Kant allows for the limitations of the transcendental and transcendent. Transcendent knowledge, under this view, is by definition beyond the ability of the human subject, while the best our cognitive advances can hope for is merely transcendental.
There seem to be several major outcomes of such a narrow epistemology that the history of philosophy has reasonably proved. First, when the noumena, or transcendent, is removed from even the possibility of knowledge and instead understood as the limitations of knowledge, metaphysics is completely removed from philosophical inquiry. The ramifications of such a removal are too vast for this brief summary, but certainly ought not to be overlooked. Second, such an epistemological model centers on the subjective ‘I,’ starting the epistemological process with the condition of a something relative to the subject, namely existence. Operating within such an internal psychological state, it is no wonder Kant has such a problem with the transcendent. Moreover, by limiting the self as ultimately elusive and unknowable the self becomes itself a phenomenon, merely an appearance of the noumena. And, under such a position, it would seemingly be impossible to ever gain knowledge of that subjective self in relation to others or objects, as others and objects would also be mere phenomena, in which case it would be impossible to even postulate the noumena.
