extent. As, however, metaphysical principles, whether valid or not, are of the same kind as we find in other rational sciences, Kant brings the problem of pure reason, which no doubt was forced upon him by metaphysics, under the general formula, How are a priori synthetic judgments possible? On the solution of this problem depends the life or death of metaphysics. For, that such a science veritably exists, no one can avouch who has considered its essential aim and observed the ill progress hitherto made by metaphysical systems. That pure mathematic and physic exist as sciences, nobody doubts. That they are possible, is proved by their actuality. And we shall only have to ask, How they are possible? But with reference to metaphysics, we shall have to settle whether reason, in pretending to tell us something of suprasensible objects, does not go beyond its own powers, and if so, what are its limits, and above all, what impels it, as by a universal and natural necessity, to go beyond those limits in quest of unattainable realities. The general problem of pure reason, How are a priori synthetic judgments possible? may, accordingly, be divided into four other questions:
1. How is pure mathematic possible?
2. How is pure physic (science of nature) possible?
3. How is metaphysic, as a natural disposition, possible?
4. How is metaphysic, as a science, possible?
Thus Kant formulates the problem of critical philosophy. However obscure the body of the Critique may appear, the introduction is written in a style so clear, exact, and even elegant that its interpretation makes little strain upon the reader's attention. And yet it has been Kant's fate to have his problem variously rendered. In the short and definite expression which it officially received at his hands, there is little room for misapprehension. All the terms of the proposition, How are a priori synthetic judgments possible? seem perfectly clear and unambiguous. Yet it ought to be noticed that, by his own confession with regard to metaphysics, Kant cannot omit the inquiry, When are a priori synthetic judgments valid? But if any one chooses to find this question implied in
