Front Page Titles (by Subject) Section I: Of the Highest Principle of all Analytical Judgments - Critique of Pure Reason
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Section I: Of the Highest Principle of all Analytical Judgments - Friedrich Max Müller, Critique of Pure Reason 
Immanuel Kant’s Critique of Pure Reason. In Commemoration of the Centenary of its First Publication. Translated into English by F. Max Mueller (2nd revised ed.) (New York: Macmillan, 1922).
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Of the Highest Principle of all Analytical Judgments
Whatever the object of our knowledge may be, and whatever the relation between our knowledge and its object, it must always submit to that general, though only negative condition of all our judgments, that they do not contradict themselves; otherwise these judgments, without any reference to their object, are in themselves nothing. But although there may be no contradiction in our judgment, it may nevertheless connect concepts in a manner not warranted by the object, or without there being any ground, whether a priori or a posteriori, to confirm such a judgment. A judgment may therefore be false or groundless, though in itself it is free from all contradiction.
The proposition that no subject can have a [p. 151] predicate which contradicts it, is called the principle of contradiction. It is a general though only negative criterion of all truth, and belongs to logic only, because it applies to knowledge as knowledge only, without reference to its object, and simply declares that such contradiction would entirely destroy and annihilate it.
Nevertheless, a positive use also may be made of that principle, not only in order to banish falsehood and error, so far as they arise from contradiction, but also in order to discover truth. For in an analytical judgment, whether negative or affirmative, its truth can always be sufficiently tested by the principle of contradiction, because the opposite of that which exists and is thought as a concept in our knowledge of an object, is always rightly negatived, while the concept itself is necessarily affirmed of it, for the simple reason that its opposite would be in contradiction with the object.
It must therefore be admitted that the principle of contradiction is the general and altogether sufficient principle of all analytical knowledge, though beyond this its authority and utility, as a sufficient criterion of truth, must not be allowed to extend. For the fact that no knowledge can run counter to that principle, without destroying itself, makes it no doubt a conditio sine qua non, [p. 152] but never the determining reason of the truth of our knowledge. Now, as in our present enquiry we are chiefly concerned with the synthetical part of our knowledge, we must no doubt take great care never to offend against that inviolable principle, but we ought never to expect from it any help with regard to the truth of this kind of knowledge.
There is, however, a formula of this famous principle — a principle merely formal and void of all contents — which contains a synthesis that has been mixed up with it from mere carelessness and without any real necessity. This formula is: It is impossible that anything should be and at the same time not be. Here, first of all, the apodictic certainty expressed by the word impossible is added unnecessarily, because it is understood by itself from the nature of the proposition; secondly, the proposition is affected by the condition of time, and says, as it were, something = A, which is something = B, cannot be at the same time not-B, but it can very well be both (B and not-B) in succession. For instance, a man who is young cannot be at the same time old, but the same man may very well be young at one time and not young, that is, old, at another. The principle of contradiction, however, as a purely logical principle, must not be limited in its application by time; and the before-mentioned formula [p. 153] runs therefore counter to its very nature. The misunderstanding arises from our first separating one predicate of an object from its concept, and by our afterwards joining its opposite with that predicate, which gives us a contradiction, not with the subject, but with its predicate only which was synthetically connected with it, and this again only on condition that the first and second predicate have both been applied at the same time. If I want to say that a man who is unlearned is not learned, I must add the condition ‘at the same time,’ for a man who is unlearned at one time may very well be learned at another. But if I say no unlearned man is learned, then the proposition is analytical, because the characteristic (unlearnedness) forms part now of the concept of the subject, so that the negative proposition becomes evident directly from the principle of contradiction, and without the necessity of adding the condition, ‘at the same time.’ This is the reason why I have so altered the wording of that formula that it displays at once the nature of an analytical proposition.