Of course, there are philosophers who have delved into the Critique of Pure Reason and returned to tell a tale in plain prose with crisp arguments. In particular, I remember reading much of Jonathan Bennett's delightfully combative Kant's Analytic with admiration and enjoyment. But the fact that different travellers come back with such very different tales is not a great encouragement to follow them by going back to Kant yourself. After all, if the quite incompatible positions A and B can each be read into Kant by some smart and well-informed commentator, then evidently his writings can't be the best unambiguous developments of A and B. If we are interested in philosophy rather than history, and want to know which of those positions about space or causation or perception or whatever is true, then we might very reasonably think that it is better to seek out the best available modern version instead. So I for one have long since crossed Kant off my reading list.
But it's worse: at least when it comes to the Big Kantian Claims (as opposed to local discussions of particular topics) I don't really grasp the import of supposed cleaned up versions either. Some years ago, I was taking my usual cheerfully realist line on something or other, and a then colleague remarked -- with a patronizing air of scorn -- that obviously I hadn't understood how Kant had shown my sort of realism to be naive and untenable. When I asked how so, I just didn't follow the answer. And that's the trouble: Kantians intimate that their hero has revealed Deep and Difficult (nay, even Transcendental) truths which philistine naturalists fail to grasp. But they seem to have a lot of difficulty explaining these supposed insights in straightforward terms the rest of us can understand. So I simply don't "get" them.
Maddy evidently is a lot more patient about wading into the Kantian mire than I am. But in fact she ends up in much the same position: the Second Philosopher too "finds no compelling motivation for his extra-empirical [transcendental] inquiry", and also regards its supposed methods as obscure and confused.
In more detail: Maddy first distinguishes two kinds of interpretation of Kant's transcendentalism, 'harsh' and 'benign'. The harsh reading takes Kant to be making a distinction between appearances or empirical objects and things in themselves, where these are quite distinct, and the latter are "unknowable but they affect our sensibility to produce appearances, which we can and do know". The harsh reading, in Strawson's words, makes "Kant ... closer to Berkeley than he acknowledges". On the benign reading,
the appearance and the thing in itself aren't two separate items -- one mental, one extra-mental -- but a single object regarded in two different ways. ... The object as appearance is subject to our human forms and categories; it is non-mental, spatiotemporal, subject to causal laws. Thus Kant is an empirical realist, as opposed to Berkeley’s empirical idealist ... On the other hand, the object as it is in itself is not subject to our forms and categories; these are impositions of our minds, not features of the transcendental object. Thus Kant is also a transcendental idealist.So on this reading, empirical enquiry and transcendental enquiry are two kinds of investigation of the same thing.
Maddy says little about the Kant of the harsh reading (which does seem to give him an entirely unattractive and arguably incoherent position), and concentrates her discussion on the benign Kant. So what is empirical enquiry and what is transcendental enquiry? The first, according to Maddy, is just science as we know and love it:
Unlike Descartes, who thinks ordinary scientific theorizing [at least, in the then prevailing style] needs justification and revision, Kant takes scientific methods to be entirely in order, for the purposes of empirical inquiry. Kant’s message to the Second Philosopher is not that she needs to reform her empirical investigations, but that she should add to them a level of transcendental enquiry. Where Descartes is only selling a new method, Kant is promoting a new purpose.But what is this new purpose? It's here that the Second Philosopher struggles. By her lights there is just one kind of enquiry, empirically constrained, and she needs to be persuaded that there is another non-empirical level available to be pursued. What is its topic? What are its methods?
Not that she dismisses the very idea of two levels just because it is "unscientific" (for she is, as we've noted before, unhappy about attempts to police boundaries in the sort of way that suggests -- she is always open to new ideas and new methods). So she is happy enough to "respectfully ask Kant to explain what it is that his transcendental psychology studies, and how this study is to be conducted". But she doesn't find the answers persuasive.
Transcendental psychology, we are told, is the study of the nature of the discursive intellect. Sure, says the Second Philosopher, but how we do know that human cognition is discursive in the defined sense without empirical work? Ah, no, we are here engaged in an apriori enquiry: 'This transcendental reﬂection is a duty from which no one can escape if he would judge anything about things a priori’ (A263/B319). To which the Second Philosopher might well riposte, borrowing Reichenbach's words, 'The evolution of science in the last century may be regarded as a continuous process of disintegration of the Kantian synthetic a priori.' She is very unimpressed by the track-record of so-called a priori enquiries (outside, perhaps, mathematics). It seems that Kant's method for pursuing them just isn't reliable, and she hasn't been told how else transcendental enquiry is supposed to be carried out.
But surely, the Kantian will respond, there are questions about the necessary conditions that must be satisfied if the world is to be experienceable, and philosophers can surely reflect on those. The Second Philosopher needn't disagree, however: of course there are very general facts (as we've discovered them to be) about how our minds work, that have implications about what sorts of worlds can be experienced by minds like those. But she will regard the exploration of such general facts to be just part of psychology done at at a level of abstraction from implementation details: part of science, broadly construed, not part of a different enterprise done at a different level with a different methodology.
The Second Philosopher knows enough of the history of philosophy to be alert to the seductive dangers of neat dualisms, and is rightly suspicious of sales talk about two distinct levels of enquiry here, empirical and transcendental. So pending further enlightment, she rests content with her one-level, empirically constrained, mode of enquiry. And I'm with her on that!