We have still to record various fruitless attempts which have been made to prove the Principle of Sufficient Reason, mostly without clearly defining in which sense it was taken: Wolf's, for instance, in his Ontology, § 70, repeated by Baumgarten in his "Metaphysics," § 20. It is useless to repeat and refute it here, as it obviously rests on a verbal quibble. Plattner[52] and Jakob[53] have tried other proofs, in which, however, the circle is easily detected. I purpose dealing with those of Kant further on, as I have already said. Since I hope, in the course of this treatise, to point out the different laws of our cognitive faculties, of which the principle of sufficient reason is the common expression, it will result as a matter of course, that this principle cannot be proved, and that, on the contrary, Aristotle's remark:[54] λόγον ζητοῦσι ὧν οὐκ ἔστι λόγος. ἀποδείξεως γὰρ ἀρχὴ οὐκ ἀπόδειξίς ἐστι (rationem eorum quærant, quorum non est ratio: demonstrationis enim principium non est demonstratio) may be applied with equal propriety to all these proofs. For every proof is a reference to something already recognised; and if we continue requiring a proof again for this something, whatever it be, we at last arrive at certain propositions which express the forms and laws, therefore the conditions, of all thought and of all knowledge, in the application of which consequently all thought and all knowledge consists: so that certainty is nothing but correspondence with those conditions, forms, and laws, therefore their own certainty cannot again be ascertained by means of other propositions. In the fifth chapter I mean to discuss the kind of truth which belongs to propositions such as these.
To seek a proof for the Principle of Sufficient Reason, is, moreover, an especially flagrant absurdity, which shows a want of reflection. Every proof is a demonstration of the reason for a judgment which has been pronounced, and which receives the predicate true in virtue precisely of that demonstration. This necessity for a reason is exactly what the Principle of Sufficient Reason expresses. Now if we require a proof of it, or, in other words, a demonstration of its reason, we thereby already assume it to be true, nay, we found our demand precisely upon that assumption, and thus we find ourselves involved in the circle of exacting a proof of our right to exact a proof.
CHAPTER III.
INSUFFICIENCY OF THE OLD AND OUTLINES OF A NEW DEMONSTRATION.
§ 15. Cases which are not comprised among the old established meanings of the Principle.
From the summary given in the preceding chapter we gather, that two distinct applications of the principle of sufficient reason have been recognized, although very gradually, very tardily, and not without frequent relapses into error and confusion: the one being its application to judgments, which, to be true, must have a reason; the other, its application to changes in material objects, which must always have a cause. In both cases we find the principle of sufficient reason authorizing us to ask why? a quality which is essential to it. But are all the cases in which it authorizes us to ask why comprised in these two relations? If I ask: Why are the three sides of this triangle equal? the answer is: Because the three angles are so. Now, is the equality of the angles the cause of the equality of the sides? No; for here we have to do with no change, consequently with no effect which must have a cause.—Is it merely a logical reason? No; for the equality of the angle is not only a proof of the equality of the sides, it is not only the foundation of a judgment: mere conceptions alone would never suffice to explain why the sides must be equal, because the angles are so; for the conception of the equality of the sides is not contained in that of the equality of the angles. Here therefore we have no connection between conceptions and judgments, but between sides and angles. The equality of the angles is not the direct, but the indirect reason, by which we know the equality of the sides; for it is the reason why a thing is such as it is (in this case, that the sides are equal): the angles being equal, the sides must therefore be equal. Here we have a necessary connection between angles and sides, not a direct, necessary connection between two judgments.—Or again, if I ask why infecta facta, but never facta infecta fieri possunt, consequently why the past is absolutely irrevocable, the future inevitable, even this does not admit of purely logical proof by means of mere abstract conceptions, nor does it belong either to causality, which only rules occurrences within Time, not Time itself. The present hour hurled the preceding one into the bottomless pit of the past, not through causality, but immediately, through its mere existence, which existence was nevertheless inevitable. It is impossible to make this comprehensible or even clearer by means of mere conceptions; we recognise it, on the contrary, quite directly and instinctively, just as we recognize the difference between right and left and all that depends upon it: for instance, that our left glove will not fit our right hand, &c. &c.
Now, as all those cases in which the principle of sufficient reason finds its application cannot therefore be reduced to logical reason and consequence and to cause and effect, the law of specification cannot have been sufficiently attended to in this classification. The law of homogeneity, however, obliges us to assume, that these cases cannot differ to infinity, but that they may be reduced to certain species. Now, before attempting this classification, it will be necessary to determine what is peculiar to the principle of sufficient reason in all cases, as its special characteristic; because the conception of the genus must always be determined before the conception of the species.
§ 16. The Roots of the Principle of Sufficient Reason.
Our knowing consciousness, which manifests itself as outer and inner Sensibility (or receptivity) and as Understanding and Reason, subdivides itself into Subject and Object and contains nothing else. To be Object for the Subject and to be our representation, are the same thing. All our representations stand towards one another in a regulated connection, which may be determined À PRIORI, and on account of which, nothing existing separately and independently, nothing single or detached, can become an Object for us. It is this connection which is expressed by the Principle of Sufficient Reason in its generality. Now, although, as may be gathered from what has gone before, this connection assumes different forms according to the different kinds of objects, which forms are differently expressed by the Principle of Sufficient Reason; still the connection retains what is common to all these forms, and this is expressed in a general and abstract way by our principle. The relations upon which it is founded, and which will be more closely indicated in this treatise, are what I call the Root of the Principle of Sufficient Reason. Now, on closer inspection, according to the laws of homogeneity and of specification, these relations separate into distinct species, which differ widely from each other. Their number, however, may be reduced to four, according to the four classes into which everything that can become an object for us—that is to say, all our representations—may be divided. These classes will be stated and considered in the following four chapters.
We shall see the Principle of Sufficient Reason appear under a different form in each of them; but it will also show itself under all as the same principle and as derived from the said root, precisely because it admits of being expressed as above.