In the former case however I comprehend how I can know a priori these propositions concerning all the objects of external intuition. Otherwise， everything else as regards all possible experience remains just as if I had not departed from the vulgar view. But if I venture to go beyond all possible experience with my notions of space and time， which I cannot refrain from doing if I proclaim them qualities inherent in things in themselves (for what should prevent me from letting them hold good of the same things， even though my senses might be different， and unsuited to them？)， then a grave error may arise due to illusion， for thus I would proclaim to be universally valid what is merely a subjective condition of the intuition of things and sure only for all objects of sense， viz.， for all possible experience； I would refer this condition to things in themselves， and do not limit it to the conditions of experience. My doctrine of the ideality of space and of time， therefore， far from reducing the whole sensible world to mere illusion， is the only means of securing the application of one of the most important cognitions (that which mathematics propounds a priori ) to actual objects， and of preventing its being regarded as mere illusion. For without this observation it would be quite impossible to make out whether the intuitions of space and time， which we borrow from no experience， and which yet lie in our representation a priori， are not mere phantasms of our brain， to which objects do not correspond， at least not adequately， and consequently， whether we have been able to show its unquestionable validity with regard to all the objects of the sensible world just because they are mere appearances. Secondly， though these my principles make appearances of the representations of the senses， they are so far from turning the truth of experience into mere illusion， that they are rather the only means of preventing the transcendental illusion， by which metaphysics has hitherto been deceived， leading to the childish endeavor of catching at bubbles， because appearances， which are mere representations， were taken for things in themselves. Here originated the remarkable event of the antimony of Reason which I shall mention by and by， and which is destroyed by the single observation， that appearance， as long as it is employed in experience， produces truth， but the moment it transgresses the bounds of experience， and consequently becomes transcendent， produces nothing but illusion. Inasmuch therefore， as I leave to things as we obtain them by the senses their actuality， and only limit our sensuous intuition of these things to this， that they represent in no respect， not even in the pure intuitions of space and of time， anything more than mere appearance of those thin-s， but never their constitution in themselves， this is not a sweeping illusion invented for nature by me. My protestation too against all charges of idealism is so valid and clear as even to seem superfluous， were there not incompetent judges， who， while they would have an old name for every deviation from their perverse though common opinion， and never judge of the spirit of philosophic nomenclature， but cling to the letter only， are ready to put their own conceits in the place of well-defined notions， and thereby deform and distort them. I have myself given this my theory the name of transcendental idealism， but that cannot authorize any one to confound it either with the empirical idealism of Descartes， (indeed， his was only an insoluble problem， owing to which he thought every one at liberty to deny the existence of the corporeal world， because it could never be proved satisfactorily)， or with the mystical and visionary idealism of Berkeley， against which and other similar phantasms our Critique contains the proper antidote.
My idealism concerns not the existence of things (the doubting of which， however， constitutes idealism in the ordinary sense)， since it never came into my head to doubt it， but it concerns the sensuous representation of things， to which space and time especially belong. Of these [viz.， space and time]， consequently of all appearances in general， I have only shown， that they are neither things (but mere modes of representation)， nor determinations belonging to things in themselves. But the word "transcendental，" which with me means a reference of our cognition， i.e.， not to things， but only to the cognitive faculty， was meant to obviate this misconception. Yet rather than give further occasion to it by this word， I now retract it， and desire this idealism of mine to be called critical. But if it be really an objectionable idealism to convert actual thin.-Is (not appearances) into mere representations.. by what name shall we call him who conversely changes mere representations to things？ It may， I think， be called "dreaming idealism，" in contradistinction to the former， which may be called "visionary，" both of which are to be refuted by my transcendental， or， better， critical idealism.
第一章Second Part Of The Transcendental Problem： How Is The Science Of Nature Possible？
Sect. 14. Nature is the existence of things， so far as it is determined according to universal laws. Should nature signify the existence of things in themselves， we could never know it either a priori or a posteriori .
Not a priori， for how can we know what belongs to things in themselves， since this never can be done by the dissection of our concepts (in analytical judgments)？ We do not want to know what is contained in our concept of a thing (for the [concept describes what] belongs to its logical being)， but what is in the actuality of the thing superadded to our concept， and by what the thing itself is determined in its existence outside the concept.
