Immanuel Kant's Metaphysische Anfangsgrunde der Naturwissenschaft, Or Metaphysical Foundations of Natural Science, was published in 1786, which is to say between the first  and second  editions of the First Critique. I have always considered it very much a minor or secondary work by Kant, and after reading it once never went back to it. When I offered this dismissive evaluation recently, my old friend Charles Parsons, perhaps the leading expert on Kant's philosophy of mathematics, called my attention to the fact that the distinguished Kant scholar Michael Friedman had written a monumental work on the Metaphysische Anfangsgrunde, and hence that I might want to rethink my opinion of it.
This got me musing about how and why we read the works of the great philosophers. Long, long ago, when I wrote my first book, on the Transcendental Analytic of the First Critique, I observed that the distinctive mark of the truly great philosophers, it seemed to me, is that they were able to see more deeply than they could say, and refused to relinquish their grasp on that deeper insight merely to achieve surface consistency. It was therefore always worthwhile to wrestle with them, struggling to liberate the deeper insights. Since it is inevitably a matter of judgment what is deep and what is not, what is worthwhile and what is not, we keep returning to those great texts, generation after generation.
I mean, think about it. Who is far and away the greatest commentator on the works of Plato who has ever lived ? The answer is obvious: Aristotle. Not only is Aristotle the most brilliant philosopher who ever wrote about Plato, he actually studied with the man for twenty years! And yet, this fact has not stopped two thousand five hundred years of philosophers from puzzling over Plato's Dialogues, poking at them, prodding them, reinterpreting them, translating them into every imaginable language. No one would ever say to a Plato scholar who has just brought out a new book on one of the Dialogues, "Why do you bother? Aristotle already has told us what to think about that."
As for Friedman's decision to focus on what I and at least some others have thought of as a minor part of the Kant corpus, we need only remind ourselves that in the nineteenth century, there were many serious thinkers who considered the Third Critique more important than the First! In the eighteenth century in England, Cicero was taken seriously as a thinker, a judgment that I have always considered bizarre and absurd, even thought it was apparently shared by David Hume, who was, for my money, the greatest philosopher ever to write in English [his only competitor being Thomas Hobbes.]
There is a view that has gained some traction with young philosophers today that Philosophy is now a science, and need no more concern itself with its history than physicists need waste time reading Einstein's early papers. I do not share that view, needless to say, but it too has its history, and crops up every few centuries.
All of which leads me to hope that after I have passed on, there will continue to be a few readers who are able to find something of value in my first book, Kant's Theory of Mental Activity.
[By the way, when I spellchecked this post in Blogger before hitting "publish," it highlighted the word "philosophers," which I had mistyped as "philosopehrs." It suggested "flyspeck" as a correction. Do you think it was trying to tell me something?]