The World as Will and Idea (Vol. 3 of 3)

In the third chapter Schopenhauer points out that the two applications of the principle of sufficient reason distinguished by his predecessors, to judgments, which must have a ground, and to the changes of real objects, which must have a cause, are not exhaustive. The reason why the three sides of a certain triangle are equal is that the angles are equal, and this is neither a logical deduction nor a case of causation. With a view to stating exhaustively the various kinds into which the application of the principle falls it is necessary to determine the nature of the principle itself. All our ideas are objects of the subject, and all objects of the subject are our ideas. But our ideas stand to one another as a matter of fact in an orderly connection, which is always determinable a priori in point of form, and on account of which nothing that is in itself separate and wholly independent of other things can be the object of our consciousness. It is this connection which the principle of sufficient reason in its generality expresses. The relations which constitute it are what Schopenhauer calls its root, and they fall into four classes, which are discussed in the four following chapters.