Immanuel Kant use to be my most favorite philosopher, but nowadays I’m not so sure anymore. Now, I certainly think Kant is one of the most influential and important philosophers ever. For one, the “analytic” and “synthetic” distinction was first explicated by Kant in his Critique of Pure Reason. While Kant’s predecessors did talk about the distinction in terms of ideas and experience (i.e. Hume), he was probably the first to use the terms “analytic” and “synthetic” as a way to make the distinction. This distinction, whether philosophers like it or not, had such an important impact in philosophy that it has a lasting influence even up to the contemporary Analytic tradition. It even survives Quine’s challenge to the distinction, though it is no longer non-controversial. Kant also had an important influence in contemporary ethics and political philosophy. The contemporary deontological ethics, Contractualism, and John Rawls’ Theory of Justice are influenced by Kant’s views on ethics. Kant was among the few philosophers to make an innovative (though in my opinion deeply flawed) argument for Philosophy of Religion known as the Moral Argument for the existence of God. Lastly, Kant’s liberal theory of international relations which is that international trade among the republics would decrease war and bring peace is an influential theory among international relation scholars.
So Kant seems like an important philosopher, but how come he’s no longer my favorite philosopher? I acknowledge that Kant still influences me when it comes to doing ethics. While I don’t agree with Kant’s deontological views about lying, I do think that his attempt to find a principled and systematic manner to derive normative claims from some ideal rational procedure is on the right track. The categorical imperative, or more specifically the formula of humanity, seems to be on the right track though it is still far from error proof. I do disagree with him that the only morally praiseworthy motive is that which is from duty, but I digress. I think my real problem with Kant is Transcendental Idealism, which I think most philosophers, especially those who do epistemology, would find troubling.
Kant’s Transcendental Idealism is really complicated, especially given that it is written in his convoluted and long book Critique of Pure Reason. I won’t go into details about Transcendental Idealism, but it basically boils down to the distinction between the phenomenal (appearance of things or experience) and noumenal (things-in-themselves). Kant basically thinks that our mind is capable of apprehending experience in terms of a priori intuitions (i.e. space-time) and concepts (i.e. causation, substance, necessity, possibility, etc.). Our minds ultimately organize our experience according to intuitions and concepts that are innate, which is how reality appears in a certain way to us. However, Kant comes to the conclusion that ultimately we can never know the true nature of reality (noumenal) and only know our experience (phenomenal). The role of reason, for Kant, is to make postulates beyond experience such as God, soul, free-will, beginning of time, etc. However, Kant thinks that ultimately reason will come across antinomies or contradictions that will prevent it from comprehending the noumenal.
Kant’s Transcendental Idealism was pretty much an essential part of his philosophical career and it had an important influence on the philosophical tradition known as German Idealism. However, ever since the decline of German Idealism (as well as British Idealism), the influence of Kant’s Transcendental Idealism pretty much fell out of favor even among Analytic philosophers. A lot of this probably has to do with Bertrand Russell and G.E. Moore’s attempt to shift away from a philosophical tradition influenced by Kant to Analytic philosophy. In Bounds of the Senses, an Analytic Philosopher P.F. Strawson tries to salvage some essential aspects of Kant’s Transcendental Idealism. However, even Strawson wouldn’t go as far to endorse Kant’s radical claim that we can never know anything about the nature of reality. From what I know so far, the only concept from Kant’s Transcendental Idealism that is still influential is the “Transcendental Apperception” or also known as the unity of consciousness (this became apparent to me when my mentor Georges Rey talked about it in his philosophy of mind class).
So what is it about Kant’s Transcendental Idealism that turns most analytic philosophers off? As my friend Ryan Carmody pointed out, its a non-starter for contemporary epistemology, since Kant’s distinction between the noumenal and phenomenal denies that there is such thing as knowledge. Most of our knowledge is about the external world, but Kant’s distinction between phenomenal and noumenal suggests that we are never justified in believing in the external world. Kant could allow that we only know our experience that presents the external world in a certain manner, but obviously this doesn’t take as very far. Kant even denies that we can know anything about our true nature, since even our “soul” belongs to the noumenal. We can only know the phenomenal experience of ourselves, but not our true nature. So even self-knowledge goes out the window. In effect, we pretty much don’t know anything.
This was a common charge against Kant even during his time. A lot of his contemporaries accuse him of radical skepticism, which Kant denies. Even though Kant was not a radical skeptic about the existence of an external world, he comes pretty close to a radical skeptic of knowledge. In fact, I personally think Kant’s Transcendental Idealism is just a fancy version of philosophical skepticism about knowledge. This might be an uncharitable and unscholarly interpretation of Kant, which I admit given that I am not a professional Kant scholar. I did, however, read Kant’s Critique of Pure Reason (though his second edition) and some secondary sources about Kant’s Transcendental Idealism (try Henry E. Allison’s “Kant’s Transcendental Idealism”). From what I can recall, Kant didn’t deny that there is such thing as knowledge, but rather he tries to redefine knowledge within his own framework. What motivates Kant to do this is that he was responding against two strains: Dogmatism and Skepticism. Kant disagreed with rationalists and empiricists like Leibniz and Locke that we have direct access to reality through reason or experience. Kant also disagreed with philosophers who came close to denying that we have any knowledge at all (i.e. Hume). Kant called philosophers like Leibniz and Locke “dogmatists” because he was worried that they came close an optimism that we can find some ultimate answer to most philosophical questions about reality. Kant wanted to emphasize that we cannot find such an answer given our epistemic finitude. Kant also balks at radical skepticism, since he thinks we do at least have some kind of knowledge. So, Kant wants to find a middle ground between Dogmatism and Skepticism. He thinks that we do not have direct access to reality, but rather we actively construct our understanding of reality from innate concepts and intuitions. Thus, knowledge is not a passive relation to reality, but rather an activity that requires some experience.
Is Kant’s redefinition of knowledge successful? Many contemporary philosophers are trying to redefine knowledge ever since Edmund Gettier presented the Gettier problem which challenged the traditional definition of Knowledge as true justified belief. However, most of these philosophers often try to redefine knowledge in such a way that reasonably allows us to have at least some knowledge about the external world. However, Kant doesn’t bother to redefine knowledge in such a way that allows us some knowledge of the external world. Kant’s framework wouldn’t allow knowledge of the external world, but only how it appears to us. As I pointed out earlier, Kant wouldn’t even allow knowledge about our true nature, which is a big trouble for anyone who believes in an inkling of self-knowledge. Furthermore, Kant’s Transcendental Idealism suffers from a problem that can potentially render it incoherent. In fact, his friend Moses Mendelssohn probably brought it up. Kant’s Transcendental Idealism states that “causation” is an a priori concept that helps us organize our experience in causal terms. Furthermore, space and time are a priori intuitions that renders raw experience into spatial and temporal manifestation. However, if space, time, and causation are just inside our head, then how did something “out” there “cause” me to have a certain kind of experience? In order to explain how I had such an experience, I need to ascribe the very concepts and intuitions to reality. However, this is contrary to what Kant wants.
Whether or not Kant’s Transcendental Idealism succeeds in redefining knowledge is up to the reader, but I personally think it should be evident that its a non-starter for contemporary epistemology. No philosopher would want to redefine knowledge in such a way that excludes any possible knowledge of the external world. Kant’s Transcendental Idealism had its run in the history of philosophy, but it has become irrelevant to contemporary epistemology. Perhaps Kant’s Transcendental Idealism is relevant to cognitive science, since he does think that our minds have innate a priori concepts and intuitions that construct our experience in a certain manner. However, its doubtful that Kant’s Transcendental Idealism is even helpful to cognitive science given that he denies we can know anything about reality including our own minds. I still think Kant is an important philosopher, but his relevance lies mostly in contemporary Ethics, Political Philosophy, International Relations, and the Analytic-Synthetic debate (though his relevance in that debate is questionable given that his theory of analyticity is not widely accepted).