Sarisberriensis in the twelfth century, for he declares in his prologue, "quia Logicce suscepi patrocinium, Metalogicus mscriptus est liber," and never makes use of the word again. There are only four metalogically true judgments of this sort, which were discovered long ago by induction, and called the laws of all thinking ; although entire uniformity of opinion as to their expression and even as to their number has not yet been arrived at, whereas all agree perfectly as to what they are on the whole meant to indicate. They are the following:—
1. A subject is equal to the sum total of its predicates, or a = a.
2. No predicate can be attributed and denied to a subject at the same time, or a = —a = o.
3. One of two opposite, contradictory predicates must belong to every subject.
4. Truth is the reference of a judgment to something outside of it, as its sufficient reason.
It is by means of a kind of reflection which I am inclined to call Reason's self-examination, that we know that these judgments express the conditions of all thinking, and therefore have these conditions for their reason. For, by the fruitlessness of its endeavours to think in opposition to these laws, our Reason acknowledges them to be the conditions of all possible thinking : we then find out, that it is just as impossible to think in opposition to them, as it is to move the members of our body in a contrary direction to their joints. If it were possible for the subject to know itself, these laws would be known to us immediately, and we should not need to try experiments with them on objects, i.e. representations. In this respect it is just the same with the reasons of judgments which have transcendental truth ; for they do not either come into our consciousness immediately, but only in concreto, by means of objects, i.e. of representations. In
