As I am tired of the scattering of side-problems of kantian philosophy that have to be seen in the light of the very idea behind kantian philosophy, I want to create a question covering the interpretational frameworks that are present here.

As Eckart Förster states in the prologue of his The 25 Years of Philosophy, Kant himself formulates a first sketch of critical philosophy in his Herz-letter (1772), from which I will translate a central statement by myself:

I asked myself: What is the foundation of/reason for [Grund] the relation of the perception [Vorstellung] to its object [Gegenstand]? (10:130)

Förster continues that the foundation of/reason for the relation for two situations seems to be unproblematic: Sensing means that the object invokes the perception, moral acting means invoking an object from a perception. But how can we possibly imagine a relation between a metaphysical object and a perception so that we can judge the truth-value (that is understanding the relation)? How is metaphysics possible? Another translation of Kant's own thoughts on that:

Where do these things [Dinge] come from if not through the way they affect [affizieren] us, and if these intellectual perceptions [intellektuelle Vorstellungen] rest on our internal activities, how come the correspondance they ought to have with the objects they are not invoked by? (10:131)

The problem we are confronted with, as philosophers, is grave: As nature is best described by natural sciences, how can we claim that we know anything not accessible by them?

His answer obviously is transcendental philosophy and transcendental idealism.

To end the question with the questions:

1) What philosophical schools of thought (then and now) are Kant's enemies? What are his objections against them?

2) What are his main arguments for transcendental idealism?

3) Why is he so desperate in defending freedom?

Each of them may be answered for itself, or, even better, in the light of each other. I beg you to found your answers on sources. I will answer myself in about two weeks after ending my paper about the practical part of the question.

  • 2
    I don't feel I have enough to post this as an answer so... (1) Kant's philosophy was a response to Hume's skepticism, and one can see Consequentialist ethics as opposed to Kant's Deontologist ethics. (3) I assume that the scientific worldview pushes causation which in turn rejects free will and thus raises questions about moral culpability which would undermine his ethics.
    – R. Barzell
    Commented Oct 19, 2015 at 17:06
  • I rather think that it is the part of Kant's thought which is independent of his overarching principles that speaks the most to us today. It is his exceptionally penetrating analysis of side problems, which we still encounter today but in a different phrasing, that is most valuable. As for Kant's overall project, times changed: he believed in certain knowledge, rational unity and moral imperatives, we can not. In Parting of the Ways Friedman has interesting thoughts on how the collapse of Kant's architectonic precipitated a crisis in Western philosophy, and the analytic/continental divide.
    – Conifold
    Commented Oct 20, 2015 at 2:24

3 Answers 3


There is a very good, citation-filled answer to all three of your questions. It’s called "Critique of Pure Reason." To provide a shorter answer may mean ignoring many aspects of these rather comprehensive questions.

1) Hume, the Leibnizians, Wolff, and the “Schoolmen.” I will not go into his arguments against each, but the gist of his two-pronged attack against the excesses of “Rationalism” and “Empiricism” (his own signature dichotomy) is captured in his famous phrase: “Thoughts without content (Rationalism) are empty, intuitions without concepts (Empiricism) are blind.” [CPR B76]

2) Such “arguments” could include both his stated reasons for developing his theory, as well as the many technical demonstrations of its validity. His main task, as he says, is to “explain how a priori synthetic judgments are possible.” To discover those “transcendental” principles that give prior form to all possible experience through a “critique of pure reason.” His aim is not a complete exposition of “pure reason” and its concepts, but a thoroughly grounded guide to its necessity and the limits of its validity. He divides his subject into “analytic” (logical contradictions) and “synthetic” judgments. The latter can be a posteriori (empirical knowledge) or a priori, which is, as stated, his main concern. These are the 12 deeper “categorical concepts” that make experience possible. [CPR B95] Not unlike Chomskey’s deep grammar. Because they cannot be “pointed out” or argued for directly, he “deduces” them from experiential content by abstraction, stripping away particulars until he can go no further, as when a “table” abstracts down to a “body” and even when we remove the “body” we still have its position in “space.” (Actually space and time are somewhat different categories). Much more could be said, it is horrendously complicated, and I do not “really” understand it well.

3) Given the Zeitgeist, Kant is “desperate” to defend an interpretation of “freedom” that we might call bourgeois or Goldilocks freedom, not too hot, not too cold. He wants to preserve the freedom of science and liberal institutions from dogma and authority…. and from material utilitarianism. At the same time, he dreads the open floodgates of scientific skepticism, Jacobin atheism, and DeSade-style unbridled relativism. How are morals and “practical reason” to be secured in a secular, self-liberating age? He first demonstrates that we do indeed have moral freedom in distinction from material Newtonian determinism. This freedom he describes as a “second type of causality,” and so presumably subject itself to certain nonscientific “causal” laws. [CPR B472] Being independent from material determinism, it must originate in the “transcendental” realm of the will or soul. Though we have no direct access to this realm and it is outside of spacetime causality, still we can say something about it without claiming dogmatically to “read the mind of God.” It remains subject to the laws of “pure reason.” From this Kant can derive his famous “categorical imperative,” essentially reconstituting the golden rule as a “deontic” command upon more formal logical grounds. Because this entails forsaking absolute knowledge of the noumenal realm, Kant says famously, “Hence I had to suspend knowledge in order to make room for belief.” [CPR Bxxix] For Kant, it was crucial that his work, however technical, be wholly compatible with common sense. His work tries to secure the rational grounds that allow us to live in a “scientific” age with moral guidance…and without simply dividing the two.

Needless to say, much more can be said, especially concerning question (2). I am by no means a Kant scholar (or even student) and surely know far less than the questioner, so I offer this partial answer largely to invite corrections, additions, and further answers.

  • Oh how funny your first sentence is :p The main point behind the question is that 1) I would like to have these questions considered before bashing Kant 2) Ask three people, get four interpretations, depending on what they think to be the truth. Therefore, thanks for answering, I will make a comment on contents later.
    – Philip Klöcking
    Commented Oct 19, 2015 at 19:34
  • Kant bashing? I thought bashing was reserved for the "dead dog," Hegel. Commented Oct 19, 2015 at 19:56
  • 1
    Hegel is untranslatable, anyway ;)
    – Philip Klöcking
    Commented Oct 19, 2015 at 20:09

Ad 3: Kant names at least the following sources which have prompted him to investigate the capabilites of reason and the scope of metaphysical claims.

1) In Prolegomena to Any Future Metaphysics That Will Be Able to Present Itself as a Science Kant writes in 1783:

Since the Essays of Locke and Leibniz, or rather since the origin of metaphysics so far as we know its history, nothing has ever happened which was more decisive to its fate than the attack made upon it by David Hume. (A7)

I openly confess, the suggestion of David Hume was the very thing, which many years ago first interrupted my dogmatic slumber, and gave my investigations in the field of speculative philosophy quite a new direction. (A13)

2) Kant later comments on this point and explicates that it was the problem of human freedom which interrupted his dogmatic slumber. See letter to Garve from 1798, quoted from p. 9 in Kreimendahl, Lothar: Der Durchbruch von 1769. Köln 1990 (in German)

Nicht die Untersuchung vom Dasein Gottes, der Unsterblichkeit etc. ist der Punkt gewesen von dem ich ausgegangen bin, sondern die Antinomie der reinen Vernunft: „Die Welt hat einen Anfang -: sie hat keinen Anfang etc. bis zur vierten: Es ist Freiheit im Menschen, - gegen den: es ist keine Freiheit, sondern alles ist in ihm Naturnotwendigkeit“: diese war es welche mich aus dem dogmatischen Schlummer zuerst aufweckte und zur Kritik der Vernunft selbst hintrieb, um den Skandal des scheinbaren Widerspruchs mit mir selbst zu heben.

3) In the Critique of Pure Reason Kant writes 1787:

Hence I had to suspend knowledge in order to make room for belief. For the dogmatism of metaphysics, that is, the presumption that it is possible to achieve anything in metaphysics without a preceding critique of pure reason, is the source of all that disbelief which opposes morality and which is very dogmatic. (BXXX)

According to Eckart Forster here „belief“ means „belief in God, freedom and immortality”. See Forster, Eckart: Die Vorreden. In Mohr, Georg; Willaschek, Marcus (Hrsg.): Immanuel Kant. Kritik der reinen Vernunft. 1998 (in German).

Hence Kants wants to save the fundamental concepts from traditional metaphysics. He accepts these concepts. His critique serves to defend them, not to question their qualification.

My opinion: In current philosophy such apologetic demand has lost much of its importance and interest.

  • First, thanks for this well-sourced answer. Second, I think indeed that the Garve-letter shows that the freedom was the main issue demanding justification. And how can this not be of current interest looking at neuroscience? The "holy triad" in fact is highly problematic. But it is questionable if he ever really needed God and an immortal soul in his practical or theoretical philosophy. Perhaps it is best described as a residue of dogmatism even he could not escape in his times.
    – Philip Klöcking
    Commented Oct 21, 2015 at 21:56
  • @Philip Klöcking Of course neuroscience knows about the mind-body problem and the issue of mental causation. But I consider Kant's reasoning not very helpful für neuroscience because Kant does not make any proposal concerning the mechanism underlying his view of mental causation. - At best, Kant's reasoning serves as a permanent reminder to fill the gap by a scientific explanation: Ceterum censeo ... - Like you I consider it a deserving enterprise to skip the "residue of dogmatism" and work out, how much of Kant's results can be preserved.
    – Jo Wehler
    Commented Oct 22, 2015 at 6:39
  • Perhaps the credit we have to give him is in the end for a philophical argument for why we are simply doing wrong in looking for the mechanism, because we cannot know anything about it. The dualists gap that no science nor philosophy can overcome without buying in other, worse things. Something like Plessner's openness (Offenheit) against absoluteness that prevents us from historical determination and enables us to evolve in political philosophy.
    – Philip Klöcking
    Commented Oct 22, 2015 at 8:11
  • A short comment about the source of the letter to Garve: In Akademieausgabe/Cambridge it is 12:257,32-258,3. Perhaps someone can deliver the Cambridge translation.
    – Philip Klöcking
    Commented Oct 22, 2015 at 9:35

Interesting question, I look forward to seeing your detailed answer.

1) The answer that I've seen in a few places for example the SEP/IEP is that he was responding to Humes sceptism which awoke him from his 'dogmatic slumber'; and specifically his critique of causality. However the Cambridge edition of the CPR points out that that the evidence that he'd read Hume is poor, and that he was responding to Liebniz/Wolff - on what account I'm not sure.

2) His transcendental method relies on arguing back from possibility, positioned as an a priori synthetic proposition to conditions.

In the first section of the critique, in the Tr. Aesthetic he argues for the Tr. Ideality of space and time so that mathematics is possible, geometry (space) and counting (time).

In the second, the Tr. Analytic he uses the categories to further ground the possibility of knowledge and experience; that is he asks how are a priori synthetic propositions of science are possible; this is where he grounds his notion of causality contra Humes psychologism.

(I'd like to add a bit more detail to this section - but I've only looked at Kants actual critique some weeks ago; and quite to my surprise some of it began to make sense rather than wholly not).

3) Kant accounts for two kinds of cause - voluntaristic freedom and natural cause; and then ties this second to cosmological freedom. But why he is desperate to defend freedom I've no idea - was freedom under threat from Wolff/Hume, say?

More no doubt can be said, but not by me at this point; it seems if I'm reading the SEP correctly that Kants transcendental method goes only so far and can't defend transcendental ideas such as free will, the soul and God; but are in a sense neccessary as outcomes of an objectified subjectivity - his Tr. Illusion (Schein) - and for this I have the impression that here he is treading on traditional grounds and methods.

This last is interesting from a materialist/physicalist account of reality - in that these notions, if he is correct, will become manifest in some other manner or by some other means - immortal humans as AI, the Singularity as God - maybe.

  • I thought it was quite indisputable that Kant read Hume rather closely, though precisely when may be in doubt. Freedom was very much the issue of the day, and "under threat" from Newtonian determinism, moral relativism, Jacobin atheism, Humean skepticism, rationalist dogma. Kant wants to save Protestant moral freedom in order the once again properly constrain it on rational grounds. By no means "academic" in the age of the Terror. Your last paragraph is interesting, but not sure what you mean. Commented Oct 20, 2015 at 14:56
  • I wasn't trying to suggest that Kant didn't; more that he was thinking on these issues before Hume awoke him from his 'dogmatic slumber'; for the second query see this answer. Commented Oct 23, 2015 at 19:47

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