judgments of that type be exhaustively discovered and proved? Even in regard to immanent metaphysics Kant interprets the formula in both ways. This is due to his frequent confusion of immanent metaphysics with the principles of natural science. Its propositions are then regarded as given, and only their general validity calls for proof. It is, however, in the problem of ideal possibility that the essential problem of the _Critique_ lies; and that is a further reason why it cannot be adequately dealt with, save by means of the synthetic method. * * * * * =Experience.=--Throughout the _Introduction_ the term _experience_[192] has (even at times in one and the same sentence) two quite distinct meanings, (1) as product of sense and understanding acting co-operatively, and (2) as the raw material (the impressions) of sense. Considerable confusion is thereby caused. =Understanding and reason=[193] are here, as often elsewhere in the _Critique_, used as equivalent terms. Throughout the entire two first sections of the _Introduction_ to the second edition the term reason does not occur even once. As first mentioned,[194] it is taken as the source of metaphysical judgments. =General (a priori) truths have an inner necessity and must be clear and certain by themselves.=[195]--These statements are not in accordance with Kant’s new Critical teaching.[196] They have remained uncorrected from a previous way of thinking. This must be one reason for the recasting of this paragraph in the second edition. =Even with (unter) our experiences there is mingled knowledge which must be of a priori origin.=[197]--Kant is here distinguishing the _immanent a priori_, such as that involved in any causal judgment, from the _transcendent a priori_ dwelt upon in the next paragraph. The latter is expressed through metaphysical judgments, such as ‘God exists,’ ‘the soul is immortal.’ =Original concepts and judgments derived from them.=[198]--Cf. B 5-6. =Pure.=--In the title of the section the term _pure_[199] (_rein_) is, as the subsequent argument shows, taken as exactly equivalent to _a priori_. As Vaihinger notes, the adjective _apriorisch_ had not yet been invented. The opposite of pure is here empirical (_empirisch_).[200] =All our knowledge begins with experience.=[201]--This is a stronger statement than any in the corresponding paragraphs of the first edition. Had Kant proceeded to develop its consequences, he would have had to recast the entire _Introduction_, setting the problem of empirical knowledge alongside that of the _a priori_.[202] As it is, he is forced[203] to subdivide the absolutely _a priori_ into the pure and the mixed.[204] =By objects which affect (rühren) our senses. The raw material of sensuous impressions.=[205]--These incidental statements call for discussion. Cf. below, pp. 80-8, 120-1, 274 ff.