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.