## Reading Group for Kant's Prolegomena: What did he get right and/or wrong?

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I've been reading Immanuel Kant's 'Prolegomena to Any Future Metaphysics', which, as I'm sure most of you are aware, he intended as a less detailed, more readable version of his previous major work 'The Critique of Pure Reason'.

I've created this discussion because I'm interested in your views as to what he got right and/or wrong with regards to the aforementioned book.

As for my views, I'm not sure at this point, and feel I need more time to develop them by digesting the book, analysing it, contemplating it, comparing it to the views of others, and so on.

I should note that I'm not as interested in what he wrote with regards to mathematics.

If it'd be helpful, I could quote some key passages.
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Quote them if you would. I'll fire up an online edition if I can find one.
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"Prolegomena" by Immanuel Kant, 1783

Let us consider first the sources of metaphysical knowledge. The very concept of metaphysics ensures that the sources of metaphysics can’t be empirical. If something could be known through the senses, that would automatically show that it doesn’t belong to metaphysics; that’s an upshot of the meaning of the word ‘metaphysics’. Its basic propositions can never be taken from experience, nor can its basic concepts; for it is not to be physical but metaphysical knowledge, so it must lie beyond experience.

Outer experience is the source of physics properly so-called, and inner experience is the basis for empirical psychology; and metaphysical knowledge can’t come from either of these.

It is thus knowledge a priori—knowledge based on pure understanding and pure reason.

[...]

[W]e cannot rightly start by asking whether synthetic a priori propositions are possible. For there are plenty of them, really given to us with undisputed certainty; and as our present procedure involves starting with what we already know, we shall start from the premise that there is human a priori knowledge of some synthetic propositions. But then we still have to ask how this knowledge is possible, i.e. what makes it possible. When we know this, we can learn how to use such knowledge and can learn what its limits are.

Stated precisely, then, the crucial question is this:

How is it possible to have a priori knowledge of synthetic propositions?

[...]

Metaphysics stands or falls with the solution to this problem. Someone may propound his metaphysical claims as plausibly as he likes, smothering us with conclusions piled on conclusions; but if he hasn’t first answered this question properly, we are entitled to say to him:

‘This is all pointless ungrounded philosophy and false “wisdom”. You purport to be using pure reason to create a priori knowledge, not by merely analysing concepts but by making new connections that don’t rest on the law of contradiction; and you think you have insight into these connections independently of
all experience. But how do you get such insight? How can you justify your claims?’

He can’t answer by appealing to the common sense of mankind, for that isn’t evidence—it’s mere hearsay. . . .

[...]

[O]ur main problem splits into four questions, which will be answered one by one:

(1) How is pure mathematics possible?
(2) How is pure natural science possible?
(3) How is metaphysics possible in general?
(4) How is metaphysics possible as a science?

[...]

(2) How is pure natural science possible?

Nature is the existence of things insofar as it is governed by universal causal laws. If this meant the existence of things in themselves, we couldn’t know nature either a priori or a
posteriori.

One way of knowing things a priori is knowing
them through the analysis of concepts. We couldn’t know nature as it is in itself in that way, because knowledge of what things are like in themselves can never come from analytically dissecting our concepts: we aren’t asking what is contained in our concept of the thing, but rather about what is added to this concept in the reality of the thing itself.

Some synthetic propositions can be known a priori because their truth is assured by the nature of our understanding, somewhat in the way that mathematical truths can be known
a priori because our sensibility assures their truth. But this is also not applicable to the supposed ‘knowledge of nature as it is in itself’, which we are discussing. My understanding has an effect on how things appear to me, but it can’t dictate what things are like in themselves. They don’t have to conform to it; so if I am to know about things in themselves, my understanding must conform to them, not vice versa.

That means that I couldn’t know about them until they had somehow been presented to me; which is to say that I couldn’t know them a priori.

Nor could I have a posteriori knowledge—i.e. knowledge through experience—of the nature of things in themselves.

If I am to bring things under causal laws, these laws must apply to them necessarily, and experience could never show me how things must be—only what there is and how it is. So it can never teach me the nature of things in themselves.
— Kant
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Hey @Sapientia I'd also be interested in joining in the discussion. I haven't read the prolegomena but have read bits of CPR and some secondary literature. Is there anything more specific that you want to discuss? You've pretty much put up the outline of his entire project.

My overall views are that he's kind of insane. There are some extremely elaborate arguments with crazy moves left and right. I like some of his critiques of other philosophers but in the end almost everything he says is wrong/untrue.

(1) How is pure mathematics possible?
(2) How is pure natural science possible?
(3) How is metaphysics possible in general?
(4) How is metaphysics possible as a science?
— Kant
1) Some things to consider. Mathematics can be considered a language so working out whether 7+5=12 could be viewed as knowing the grammar of the language. Obviously this view would depend on your philosophy of language, but if it seems correct then 7+5=12 doesn't really fit anywhere in Kant's framework.
One of the issues is that, for Kant, formal logic had not been invented yet. His examples of analytic truths (as far as I can remember) are of the form A=P&Q (Bachelor = Unmarried Man) Therefore if I know A I know P, and I know Q. In logic we use many more rules than this, so Kant's 'analytic' definition is quite limited.

I could comment on 2)3)&4) but I don't think they are possible in the way that Kant thinks they are. Not sure what you are looking for. You probably need to focus the thread more for people to get involved.
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Not sure what you are looking for. You probably need to focus the thread more for people to get involved.

Thanks for your reply, and for the advice above. Maybe I'll start near the beginning, and break things down as I go forward.
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To start with, his definition of "metaphysics" seems problematic. Although his explanation for defining metaphysics the way that he does makes some sense, it seems too restrictive, yet restrictive in a way that's convenient for his argument.

Metaphysics is often summed up, as it has been on this site, as asking "big questions", regarding things like truth and reality, and including questions such as "What exists?" and "Are objects constituted by the way we see and describe the world?".

If such questions are appropriate in metaphysics, then it seems completely wrong to exclude empiricism, that which is known through the senses, that which is taken from experience, and that which is physical. We can still question whether anything exists beyond the aforementioned, and if so, how much we can know about it - without making such an exclusion.

This criticism is only minor, I think. He wanted to write about a certain (aspect of) reality, and our possible knowledge of it, and he chose - whether right or wrong - to use the word "metaphysical".
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If such questions are appropriate in metaphysics, then it seems completely wrong to exclude empiricism, that which is known through the senses, that which is taken from experience, and that which is physical. We can still question whether anything exists beyond the aforementioned, and if so, how much we can know about it - without making such an exclusion.

But wouldn't we then say that we're doing natural science when we go by empirical evidence, but when we ask, e.g., about what is beyond them--for which there can be no evidence, for if there were we would just be doing science again--then we are doing metaphysics?

I don't know if this helps, because it's very general, but what I think Kant got right in the CPR and Prolegomena--or anyway what I like--is the transcendental insight. This is the idea that we are reciprocally coupled with the world. As far as the world is knowable, it is knowable only subject to the conditions under which it is possible for us to know anything, and as we are finite beings who experience things in our own special way, what we can come to know, and thus objects themselves, are conditioned by our way of knowing. This has been read as idealism, but it can also be seen as a way between realism and idealism:

When we ask the constitutional question of how objects are disclosed to us, then any object, including any scientific object, must be regarded in its correlation to the mental activity that intends it. This transcendental orientation in no way denies the existence of a real physical world, but rather rejects an objectivist conception of our relation to it. The world is never given to us as a brute fact detachable from our conceptual framework. Rather, it shows up in all the describable ways it does thanks to the structure of our subjectivity and our intentional activities. — Evan Thomson, Mind in Life
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But wouldn't we then say that we're doing natural science when we go by empirical objects etc., but when we ask, e.g., about what is beyond them--for which there can be no evidence, for if there were we would just be doing science again--then we are doing metaphysics?

But why can't (or shouldn't) the two overlap? Natural philosophy is a branch of philosophy, after all. Based solely on the meaning of the component parts that make up the word "metaphysics", it makes sense to exclude physics, but is that a good enough reason to do so? It might be more productive to include it. I think I'd prefer a more open and inclusive approach to the sort of questions that spring up in metaphysics than an approach which isolates metaphysics and excludes natural science.
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Are you saying this from the point of view of someone thinking about how best to do metaphysics? In saying that metaphysics is non-empirical, Kant is not saying that it ought to be so; he's just defining it. It's more accurate to describe Kant as excluding metaphysics from natural science. Part of his whole project in the CPR is to save a sliver of legitimate metaphysics by ditching the rest, at the same time as proving the objective validity of physics. (Sorry, don't have much time for this right now)
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I spent a long time reading Kant, and ultimately I think I have no major sympathies with him.

If you want an extremely reductive dismissal of his work, here is how I feel about it: it all consists of taking analytical prejudices and claiming that they're necessary. This is so insofar as the 'common wisdom' of the age is taken to be something that arose necessarily, and so the prejudices that underly it have to be traced backward and declared the ultimate source of all things (since the way we see things now is therefore the way they must always be seen). In short, Kant is the 'mythologizer' par excellence. His business was creating etiological myths about how the world as he knew it came to be, like the story of Jacob and Esau and the red soup, and how what must have happened in order to reach that state therefore had to have a divine or permanent status.

I think there is really little else to say about him.
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I could comment on 2)3)&4) but I don't think they are possible in the way that Kant thinks they are. Not sure what you are looking for. You probably need to focus the thread more for people to get involved.

Please do so. Why aren't they possible in the way that Kant thinks they are? We could focus on 2) for starters. I have already quoted the first part of that chapter which contains an argument. I've also provided a link to an online version of the book.

If you want an extremely reductive dismissal of his work, here is how I feel about it: it all consists of taking analytical prejudices and claiming that they're necessary. This is so insofar as the 'common wisdom' of the age is taken to be something that arose necessarily, and so the prejudices that underly it have to be traced backward and declared the ultimate source of all things (since the way we see things now is therefore the way they must always be seen). In short, Kant is the 'mythologizer' par excellence. His business was creating etiological myths about how the world as he knew it came to be, like the story of Jacob and Esau and the red soup, and how what must have happened in order to reach that state therefore had to have a divine or permanent status.

I think there is really little else to say about him.

You might be right, but I don't know what exactly you're referring to. Some examples would help. What analytical prejudices? And where does he claim that they're necessary? What's this myth that he allegedly created about how the world as he knew it came to be?
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You might be right, but I don't know what exactly you're referring to. Some examples would help. What analytical prejudices? And where does he claim that they're necessary? What's this myth that he allegedly created about how the world as he knew it came to be?

So, for example, Kant thought that (Aristotelian) logic was complete, and so derived a table of categories that were necessary to all thought on the basis of the sorts of tables logicians would draw up. That is, in a way, all he does, with various disciplines.
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I want to revisit this work in light of your thread.

As a general thrust, however: I have only just begun to disagree with Kant, and I'm still uncertain on which ways I am confident to do so. Saying that, however, I think it is invaluable to read him as if you agree with him and attempt to understand him from his own perspective. Part of my project to disagree with Kant was the hope that I might disagree with him in a way that he might hypothetically agree with -- meaning that I might understand where he's coming from, and would be able to say why I disagree in his own idiom [even if my own personal philosophical interests might differ]
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It strikes me this discussion would work well as a more formal reading group, especially if @Moliere is on board. So, you'd agree to read a section at a time and post your thoughts, that kind of thing. What do you think, @Sapientia?
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Sure. Why not? I don't mind if this discussion is moved to the reading group category.
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Done.

I suggest first reading the Preface ("Introduction" in Bennett's version) and Preamble and then comparing notes. Looks like you're already there @Sapientia; it might take others a while to catch up. I will try to take part.
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I've found the following to be useful resources:

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When I was reading the CPR I found this glossary of Kant's technical terms extremely useful:

http://staffweb.hkbu.edu.hk/ppp/ksp1/KSPglos.html
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Here’s my bit about the preface. I’m just going to ramble on because it feels good, like going for a bike ride for the first time in months.

Preface or Introduction

First, I like that it's well-written, which is not something Kant is famous for. But he could do it if he tried, and he thought it especially important to boost the rhetoric and drama for this particular book. The Prolegomena was written a couple of years after the publication of the first edition of the Critique of Pure Reason, and was intended as a forceful summary of that work. Kant is on a mission to reform metaphysics, and this book is meant to serve as the starting point for all future attempts at doing it. What this really means is that he is attacking traditional rationalist metaphysics.

Metaphysics was, or was felt to be, in crisis. In contrast to physics, which had been making great strides of discovery for a couple of hundred years and which had recently been revolutionized by Newton, metaphysics “cannot, as other sciences, attain universal and lasting acclaim”, and “perpetually turns round on the same spot without coming a step further”. Back then, in the midst of the Enlightenment, any endeavour aiming at knowledge of the world was expected to make progress. But there was no such progress in metaphysics, nor even any substantial agreement. Kant is saying, “if you think you can do metaphysics, read this first before embarrassing us all.”

The particularly philosophical source of the crisis of metaphysics was David Hume’s scepticism, and Kant makes it explicit here that the construction of the CPR was based on the need to respond to him. Kant nicely summarizes Hume’s position on the connection of cause and effect:

He indisputably proved that it is wholly impossible for reason to think such a connection a priori and from concepts, because this connection contains necessity; and it is simply not to be seen how it could be, that because something is, something else necessarily must also be, and therefore how the concept of such a connection could be introduced a priori. From this he concluded that reason completely and fully deceives herself with this concept, falsely taking it for her own child, when it is really nothing but a bastard of the imagination, which, impregnated by experience, and having brought certain representations under the law of association, passes off the resulting subjective necessity (i.e., habit) for an objective necessity (from insight). From which he concluded that reason has no power at all to think such connections, not even merely in general, because its concepts would then be bare fictions, and all of its cognitions allegedly established a priori would be nothing but falsely marked ordinary experiences; which is so much as to say that there is no metaphysics at all, and cannot be any.

This is a threat in two specific ways. It questions the possibility of metaphysics as an independent science (a rigorous, rational and progressive discipline), and it also threatens the status of physics insofar as physics is based on principles and laws that are meant to apply without fail, necessarily and throughout the universe, e.g., Newton's Laws or Einstein's equation of general relativity; or based on more basic metaphysical principles such as that every event is caused. Reason (the a priori) is independent of the empirical, but it often concerns itself with the empirical. So in a nutshell, Hume had threatened humanity’s claim to rational objective knowledge.

Kant, unlike Hume, is going to defend reason’s ability to apply a priori concepts of necessity and universality; he will say that this is much more than just a habit to get us through life. But to do this he will drastically restrict the domain over which this can be done. Basically [SPOILER ALERT!] the answer will be that informative objective a priori knowledge is possible, but only when it concerns the objects of experience, i.e., speculative metaphysics is impossible. These are the positive and negative aspects of Kant’s project, respectively: in support of our ability to know the world objectively through physics and natural science more generally, but against the attempt to get beyond experience.

A word about metaphysics to clarify what I’ve just been saying, and this might also help to solve @Sapientia's worry about the separation of metaphysics and the empirical. For Kant there are basically two kinds: immanent metaphysics or the metaphysics of experience and transcendent or speculative metaphysics. (Note it’s transcendent and not transcendental). Immanent metaphysics is a priori reasoning concerning the objects of experience and thus the objects of physics; it’s basically about the “principles and laws” I mentioned, on which natural science is based. Speculative metaphysics, on the other hand, is a priori reasoning about what is beyond experience. It’s about what the world is really made of beyond any evidence we could possibly adduce. Examples are Leibniz’s monads and Plato's theory of forms. Speculative metaphysics is pretty much what we mean by metaphysics today.

However, although it's not quite clear at this stage there is really another kind of metaphysics: that which Kant himself is going to be doing, which is transcendental metaphysics, which explores the relationship of human reason and experience with the world. On the other hand it's debatable if this is metaphysics or in fact just epistemology. Anyway, I expect there will be more about that in later posts.

Metaphysics is often summed up, as it has been on this site, as asking "big questions", regarding things like truth and reality, and including questions such as "What exists?" and "Are objects constituted by the way we see and describe the world?".

If such questions are appropriate in metaphysics, then it seems completely wrong to exclude empiricism, that which is known through the senses, that which is taken from experience, and that which is physical. We can still question whether anything exists beyond the aforementioned, and if so, how much we can know about it - without making such an exclusion.

I think we can now see that Kant is not excluding the empirical. Metaphysics can be about empirical objects--it is just that they cannot be the source of metaphysical knowledge, just as Hume showed.

I don't have any comments on what he got right and wrong, because I think it's too early for that.

Next I’ll cover the Preamble, which is mainly about the analytic-synthetic distinction. A priori-a posteriori should probably be sketched out too.
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Already it's been a pleasure to revisit Kant. Thanks for the opportunity @Sapientia , and the suggestion to do this reading-group style @jamalrob

Preface

The preface states who the work is meant for -- not for apprentices of metaphysics who are just learning the ropes, not for historians of philosophy who must wait for the philosophers and scientists proper to create the new science he has in mind, not for those who look at the works of metaphysics in dismay, contempt, or of an attitude firmly decided on such questions by way of ancient authority -- but for those future teachers and founders of a science who already believe metaphysics is a worthwhile pursuit unto itself, and who might become lost in reading the proper treatment of the subject due to the self-admittedly literary weakness that academic requirements make of any work in that vein -- and who want a guide to begin understanding his arguments so that they may fruitfully pursue metaphysics, and hopefully ground it as a proper scientific discipline, or barring that, show in what other manner Hume's critique of knowledge may be successfully addressed.

As such we find the thesis of the Prolegomena in paragraph 7:

... there can be no such science unless the requirements expressed here, on which its possibility rests, are met, and, as this has never yet been done, that there is as yet no metaphysics at all — Kant

I separated out the previous quote for emphasis, though this immediately follows:

Since, however, the demand for it can never be exhausted, because the interest of human reason in general is much too intimately interwoven with it, the reader will admit that a complete reform or rather a rebirth of metaphysics, according to a plan completely unknown before now, is inevitably approaching, however much it may be resisted in the meantime

I quote this to emphasize in what way Kant's work is meant as a propaedeutic to metaphysics.And so, in some ways, what we are dealing with in the Prolegomena is -- as far as explicit intent is concerned, at least -- something of a propaedeutic to the propaedeutic proper.

To emphasize this reading I would point a few pages later, after he gives some history of the problem he's dealing with (including his own struggles with it):

But I fear that the elaboration of the Humean problem in its greatest possible amplification (namely, the Critique of Pure Reason) may well fare just as the problem itself fared when it was first posed

. . .

with regard to a certain obscurity -- arising in part from the expansiveness of the plan, which makes it difficult to survey the main points upon which the investigation depends -- in this respect the complaint is just; and I will redress it through the present Prolegomena.
The previous work, which presents the faculty of pure reason in its entire extent and boundaries, thereby always remains the foundation to which the Prolegomena refer only as preparatory exercises; for this Critique must stand forth as science, systematic and complete to its smallest parts, before one can think of permitting metaphysics to come forward, or even of forming only a distant hope for metaphysics

Something that piqued my interest later is when Kant distinguishes between methods to draw the distinction between the Prolegomena and the Critique -- namely, the Prolegomena follows the analytic method, and the Critique follows the synthetic method. Kant insists that the synthetic method is necessary to present all the articulations, whereas the analytic method is good enough -- after accepting the deduction (which, back then, was more akin to legal justification than dedeuctive logical inference) -- for giving the plan in broad strokes.

Lastly, I want to highlight one quote at the end to show what Kant is asking of his readers. In part it articulates what we mean today by "inference to the best explanation", I think -- which Kant is sometimes credited with articulating -- but historically speaking it's what makes Kant's philosophy truly critical, as opposed to either dogmatic or skeptical:

whosoever undertakes to judge or indeed to construct a metaphysics, must thoroughly satisfy the challenge made here, whether it happens that they accept my solution, or fundamentally reject it and replace it with another

(emphasis mine)

So our job isn't to just find why we disagree with Kant -- because, indeed, it's easy to see that everyone except Kant disagrees with Kant ;) -- but to judge whether we do, in fact, agree, and if we do not, to not fall into skepticism and present our own solution.
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Nice post @Moliere. One thing I avoided when writing my own summary was this:

Something that piqued my interest later is when Kant distinguishes between methods to draw the distinction between the Prolegomena and the Critique -- namely, the Prolegomena follows the analytic method, and the Critique follows the synthetic method. Kant insists that the synthetic method is necessary to present all the articulations, whereas the analytic method is good enough -- after accepting the deduction (which, back then, was more akin to legal justification than dedeuctive logical inference) -- for giving the plan in broad strokes.

Can you say more about what he means by this? I was never quite sure.
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Right, I wrote this too so I'll post it. Then I'll hold off for a while. And if anyone thinks these walls of text aren't suitable for the thread, let me know. I've written so much because I've been enjoying it.

Preamble

The Preamble covers the central distinction covered in the introduction to the CPR, between analytic and synthetic judgements. He begins in section 1 by looking at the sources of metaphysical knowledge, and states that they are a priori by definition.

A few words about a priori and a posteriori. These are about justification, i.e., how we come to know things, so they are epistemological concepts. In the CPR Kant says that “There can be no doubt that all knowledge begins with experience”, but that “although our knowledge begins with experience, it does not follow that it arises from experience.” What this means is that it is experience that calls forth knowledge, not that it is the source. For example, it is in experience that we come to know about cause and effect in the first place, but only because events must be experienced in terms of a prior, independent (pure) concept of the understanding.

The crucial thing to know about the a priori is that it is characterized by necessity and universality. In contrast to empirical knowledge, which is always contingent--it only happens to be the case that the sun rose this morning--and applies only as far as we know to the cases we can observe, a priori knowledge is what is always applied to everything that is relevant to it, everywhere and for all time. Thus we generalize from observation into laws, e.g., every event has a cause, the total mass-energy of a closed system remains constant, and E=mc^2.

All necessary truths must be known a priori, because experience and induction can only give us contingency as Hume showed. E=mc^2, for example, might at first sight look like it's a posteriori, because it's confirmed by experiment. But all that's really discovered in such an experiment is that E=mc^2 happened to be true on that occasion; the necessity and universality of the equation, it's law-like character, cannot be confirmed by experience.

But is all a priori knowledge necessary? Historically most philosophers have thought so--it’s hard to think of anything a priori that doesn’t apply across the board necessarily. But Kripke argued that there is such a thing as contingent a priori knowledge. However I’ll leave that aside, because it’s is not the kind of a priori that Kant is interested in.

It’s often said that Kant found a way between rationalism and empiricism, or a way to reconcile them, and it can be seen here. The rationalists had their innate ideas, like the ideas that God is omnipotent or that time has no beginning and no end, which are thought to be necessary and universal. But Kant's a priori knowledge is different: it consists of concepts or principles that are used to form judgements about the objects of experience, whereas the innate ideas are whole judgements already present in the mind and complete without any experience at all. Thus Kant accepts that experience is essential for knowledge (empiricism), but also accepts that necessary and universal truths can be known by the understanding (rationalism).

Briefly on this point, I think it's wrong to think of rationalism and empiricism here as equal, competing philosophies. Kant was in the rationalist tradition and, in a way, wanted to save it from scepticism by reforming it. Adorno puts it nicely in his lectures on the CPR:

...the synthetic a priori, in short, the incontrovertibly true and valid modes of knowledge that far surpass mere logic, may be described as the roast, the Leibnizian or Cartesian roast, while Hume and English scepticism provide the dialectical salt. — Theodor Adorno

Section 2 is about the types of knowledge that can be called metaphysical. Whereas the a priori-a posteriori distinction concerns how we know things, this is about what we know. In other words, a priori-a posteriori is about the justification of propositions and analytic-synthetic is about the character of the propositions themselves, or about the sort of truths they are, or more precisely what makes them true or false. Whereas a priori-a posteriori is epistemological, analytic-synthetic is semantic.

So Kant makes a distinction between judgements (we can think of judgements as propositions held to be true in human understanding), and this distinction applies to all judgements, whether they contribute a priori or a posteriori knowledge:

• Analytic: explicative judgements, ones that don’t tell us anything new but just bring out what’s already there.
• Synthetic: ampliative judgements, ones that are informative, i.e., they add something new.

Analytic judgments. Kant uses something like the containment metaphor he used in the CPR to define these. This is the idea that the subject of a proposition contains the predicate already, e.g., in “All bachelors are unmarried”, being unmarried is contained in the concept of a bachelor. In contrast, “Some bachelors are Mexican” is not analytic because the concept of bachelors has nothing to do with being Mexican.

Incidentally, the example he actually uses, of bodies being extended (analytic) and heavy (synthetic), is much less useful to us now. At the time, extension was a part of the concept of a material body (meaning a physical thing), both in physics and metaphysics, whereas weight was not. He was just using a familiar and uncontroversial concept.

He goes on to elaborate on his containment definition: an analytic judgement is one whose negation is a contradiction. Thus it is contradictory to deny that all bachelors are unmarried.

It’s easy to get a sense of what “analytic” means from this, but it’s a bit vague, and later philosophers--who had better logical tools than Kant, who was working with Aristotle’s logic--pointed out that his definitions are not general enough. For example, he has only really covered subject-predicate propositions, but he means analyticity to apply to more complex judgements, like those involving conditionals.

There are other logical problems, but it turns out that analyticity can be satisfactorily generalized:

A judgement and its negation are both analytic if and only if one of the pair is self-contradictory, or false by virtue of the definitions of words or its logical form. — Jill Vance Buroker

In any case, I find true by definition or true by virtue of the meanings of the constituent terms to be close enough approximations much of the time.

As Kant points out at the end of 2(b), all such judgements must also be a priori, because it is logical form and the definitions of the terms involved that determine whether they’re true or false--not experience.

Synthetic judgments. These can be defined as simply the contrary of analytic judgements, i.e., they are judgements that are not true by virtue of the meanings of the constituent terms. So it’s clear enough that a posteriori judgements, i.e., judgements of experience, are all synthetic. But Kant says there are synthetic a priori judgements too.

He classifies synthetic judgements like this:

1. Judgements of experience
2. Mathematical judgements
3. Properly metaphysical judgements

I’ve said enough about 1. And like @Sapientia I don’t feel like covering the mathematics, whether 7 + 5 = 12 is synthetic or not, etc. My feeling has always been that mathematics is entirely analytic and that Kant was wrong on this. I don’t know how badly that damages Kant’s project--I suspect it doesn’t.

So that leaves metaphysics. Here he argues that although there are analytic judgements in metaphysics--I think of these like steps in solving a mathematical equation--the important ones are synthetic. Just like physics, with its propositions such as “air is an elastic fluid”, the whole point of metaphysics is to tell us something about reality, something that is not true only by definition. He gives the example that “all that is substance persists”, which is a conservation principle that serves as a foundation for physics (the quantity of matter remains constant in physical interactions). Other more controversial synthetic judgements of metaphysics are that reality is fundamentally made up of monads, that reality is fundamentally made up of matter, and that reality is divided between two substances, mind and matter. These aim at positive knowledge, not mere explication.

And of course they are also a priori, so we can see that the synthetic a priori will be Kant’s main concern.

So we can make a table of knowledge like this:

                  analytic            synthetic
a priori              ✓                   ✓
a posteriori          —                   ✓


There is no such thing as analytic a posteriori, because what can be known based on experience cannot be true merely by definition or logically.

That’s enough for now. The next bit, the “General Question”, is where Kant introduces the central question: How are synthetic a priori propositions possible?
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At this point it would just be speculation on my part. I'm not exactly sure. Though it seems to make sense from his examples and with his philosophy in general -- it seems that with the "analytic" method we would basically be presupposing the conclusions of the critique of pure reason and deducing their implications so that one understood the general plan. Whereas with the synthetic method we would be presenting something for someone else to judge -- ie the deduction -- and consider in light of reason.

That's just a guess though.

What interested me most was the relationship between method and knowledge. I checked the german real quick to make sure that the word wasn't "wissenschaft" or anything -- it was actually Methode. Usually I think of the analytic/synethic distinction as something which applies to knowledge, but here Kant mentions a method. Though that could also just be my memory, as well. It's been a minute since I've picked up the CPR, so maybe he made more of that than I had perceived or remember.
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I thought that his use of analytic/synthetic to describe the different methods of the Prolegomena and the CPR respectively was mostly unrelated to his use of it to describe judgements. Isn't it more about analytic as in breaking down a complex whole, and synthetic meaning building up from basic elements? But I'm not really sure how that applies to the books, unless he's simply saying that in the CPR he had to start from scratch and build the edifice brick by brick, and that in the Prolegomena he is taking this already built thing and breaking it down to reveal its core truths.
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That's what I took him to be saying in the preface. And I could see there being no relation between the analytic/synthetic method and knowledge. It was just something that caught my eye is all.
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The General Question

Section 4

Is metaphysics possible at all?

If Hume was right, the answer to this is no. And there wasn't much evidence to the contrary, as Kant notes:

One can point to no single book, as for instance one presents a Euclid, and say: this is metaphysics, here you will find the highest aim of this science, knowledge of a supreme being and a future life, proven from principles of pure reason.

The crucial point of this section is toward the end. Although he cannot yet answer whether metaphysics as a science* is possible, he can say with confidence that synthetic a priori knowledge is at least possible in mathematics and physics. The basic laws of physics, as I discussed in my last post, are synthetic a priori because they are ampliative, necessary and universal, and not strictly determined by empirical discoveries.

*Again note that "science" in Kant's day meant a systematic body of knowledge and the practices that contribute to it.

Since metaphysics aims at informative knowledge established with the use of pure reason, it aims at synthetic a priori knowledge. And since synthetic a priori is possible, we need to find out how it is possible...

...in order to be able to derive, from the principle of the possibility of the given cognition, the possibility of all other synthetic cognition a priori.

Section 5

The heading of this section is How is cognition from pure reason possible? Kant calls this the popular version of the central question, How are synthetic propositions a priori possible?. ("Cognition", by the way, is the currently favoured translation of Erkenntnis, also sometimes translated as "knowledge". There are many cases where I suspect "knowledge" is a better translation, but that's mainly a gut feeling.)

He restates the main point:

...synthetic but pure rational cognition is actual; but we must nonetheless next investigate the ground of this possibility, and ask: how this cognition is possible, so that we put ourselves in a position to determine, from the principles of its possibility, the conditions of its use and the extent and boundaries of the same. Expressed with scholastic precision, the exact problem on which everything hinges is therefore:

How are synthetic propositions a priori possible?

Some other ways of putting the question:

In short, how can there be ampliative or informative judgments that are nevertheless necessarily true? This is the technical problem driving the critical philosophy — Jill Vance Buroker

When Kant asks the question “how are synthetic a priori judgements possible?” he is asking “how is it possible for thought to generate something new?” — Levi Bryant

Kant brings up the threat of Hume again to emphasize the importance of the question:

For how is it possible, asked the acute man, that when I am given one concept I can go beyond it and connect another one to it that is not contained in it, and can indeed do so, as though the latter necessarily belonged to the former? Only experience can provide us with such connections (so he concluded from this difficulty, which he took for an impossibility), and all of this supposed necessity – or, what is the same – this cognition taken for a priori, is nothing but a long-standing habit of finding something to be true and consequently of taking subjective necessity to be objective.

In my first post I wondered about the status of Kant's own critical philosophy with respect to metaphysics. Although he has described what he is doing as a new science, here in this section is the first explicit mention and description of transcendental philosophy:

It can be said that the whole of transcendental philosophy, which necessarily precedes all of metaphysics, is itself nothing other than simply the complete solution of the question presented here, but in systematic order and detail, and that until now there has therefore been no transcendental philosophy; for what goes under this name is really a part of metaphysics, but this science is to settle the possibility of metaphysics in the first place, and therefore must precede all metaphysics.

He thus reserves a very special place for his own philosophy. This is not just a competing theory of reality; it is an account of the very conditions of the possibility of philosophy and all other knowledge. In a letter to Marcus Herz he called it a “metaphysics of metaphysics”.

But hasn't he already said that before attempting metaphysics you have heed the doctrine of transcendental philosophy? So how could he have legitimately carried through a “metaphysics of metaphysics”? If transcendental philosophy is a kind of metaphysics, how can he guarantee that, being originally ignorant of what he finally discovered, he happened upon the right method and the right answers?

The answer is that most of the time he is talking about traditional ontology, which theorizes about the nature of reality as it is outside of the conditions under which human beings can know it. In contrast, his metaphysics is something very special, something nobody had attempted before. In transcendental philosophy one works back to uncover the conditions that must hold for knowledge to be possible:

I call all cognition transcendental that is occupied not so much with objects but rather with our mode of cognition of objects insofar as this is to be possible a priori. A system of such concepts would be called transcendental philosophy.

This is of course an epistemological question, but this surely isn't just epistemology, because in answering it he does much more than describe how we access a given, assumed reality; rather, he assigns new, original status to reality, objects, space and time, and human consciousness.

Back to the central question, what he now begins to call the "main transcendental question". Since we know that synthetic a priori knowledge is possible in mathematics (setting aside objections for now) and physics, he is going to deal with those first before proceeding on to metaphysics. Thus he breaks down the question like this:

1. How is pure mathematics possible?
2. How is pure natural science possible?
3. How is metaphysics in general possible?
4. How is metaphysics as science possible?

But what exactly is "pure natural science"? If we read this in line with everything that's gone before, it must be the a priori component of physics, roughly corresponding with fundamental mathematical physics as opposed to experimental physics.

But I am still a bit confused about this. Is pure natural science to be identified with immanent metaphysics, i.e., the metaphysics of experience, or is that the legitimate separate discipline of metaphysics? Where does physics end and metaphysics begin? Is that the wrong question? Looking ahead to the section itself, he says the following:

pure natural science, which, a priori and with all of the necessity required for apodictic propositions, propounds laws to which nature is subject.

Perhaps we should remember that the rift between physics and philosophy was not then so wide as it is now, and the thought that physicists were engaging in metaphysics as part of their work was not unusual.

Next, things get tricky.
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