are ideas of reason； which cannot be given in any experience。 Only we are not here concerned with the theoretical knowledge of the objects of these ideas； but only with this； whether they have objects at all。 This reality is supplied by pure practical reason； and theoretical reason has nothing further to do in this but to think those objects by means of categories。 This； as we have elsewhere clearly shown； can be done well enough without needing any intuition （either sensible or supersensible） because the categories have their seat and origin in the pure understanding； simply as the faculty of thought； before and independently of any intuition； and they always only signify an object in general； no matter in what way it may be given to us。 Now when the categories are to be applied to these ideas； it is not possible to give them any object in intuition； but that such an object actually exists； and consequently that the category as a mere form of thought is here not empty but has significance； this is sufficiently assured them by an object which practical reason presents beyond doubt in the concept of the summum bonum； the reality of the conceptions which are required for the possibility of the summum bonum； without； however； effecting by this accession the least extension of our knowledge on theoretical principles。
When these ideas of God； of an intelligible world （the kingdom of God）； and of immortality are further determined by predicates taken from our own nature； we must not regard this determination as a sensualizing of those pure rational ideas （anthropomorphism）； nor as a transcendent knowledge of supersensible objects； for these predicates are no others than understanding and will； considered too in the relation to each other in which they must be conceived in the moral law； and therefore； only so far as a pure practical use is made of them。 As to all the rest that belongs to these conceptions psychologically； that is； so far as we observe these faculties of ours empirically in their exercise （e。g。； that the understanding of man is discursive； and its notions therefore not intuitions but thoughts； that these follow one another in time； that his will has its satisfaction always dependent on the existence of its object； etc。； which cannot be the case in the Supreme Being）； from all this we abstract in that case； and then there remains of the notions by which we conceive a pure intelligence nothing more than just what is required for the possibility of conceiving a moral law。 There is then a knowledge of God indeed； but only for practical purposes； and； if we attempt to extend it to a theoretical knowledge； we find an understanding that has intuitions； not thoughts； a will that is directed to objects on the existence of which its satisfaction does not in the least depend （not to mention the transcendental predicates； as； for example； a magnitude of existence； that is duration； which； however； is not in time； the only possible means we have of conceiving existence as magnitude）。 Now these are all attributes of which we can form no conception that would help to the knowledge of the object； and we learn from this that they can never be used for a theory of supersensible beings； so that on this side they are quite incapable of being the foundation of a speculative knowledge； and their use is limited simply to the practice of the moral law。 This last is so obvious； and can be proved so clearly by fact； that we may confidently challenge all pretended natural theologians （a singular name）* to specify （over and above the merely ontological predicates） one single attribute； whether of the understanding or of the will； determining this object of theirs； of which we could not show incontrovertibly that； if we abstract from it everything anthropomorphic； nothing would remain to us but the mere word； without our being able to connect with it the smallest notion by which we could hope for an extension of theoretical knowledge。 But as to the practical； there still remains to us of the attributes of understanding and will the conception of a relation to which objective reality is given by the practical law （which determines a priori precisely this relation of the understanding to the will）。 When once this is done； then reality is given to the conception of the object of a will morally determined （the conception of the summum bonum）； and with it to the conditions of its possibility； the ideas of God； freedom； and immortality； but always only relatively to the practice of the moral law （and not for any speculative purpose）。
*Learning is properly only the whole content of the historical sciences。 Consequently it is only the teacher of revealed theology that can be called a learned theologian。 If； however； we choose to call a man learned who is in possession of the rational sciences （mathematics and philosophy）； although even this would be contrary to the signification of the word （which always counts as learning only that which one must be 〃learned〃 and which； therefore； he cannot discover of himself by reason）； even in that case the philosopher would make too poor a figure with his knowledge of God as a positive science to let himself be called on that account a learned man。
According to these remarks it is now easy to find the answer to the weighty question whether the notion of God is one belonging to physics （and therefore also to metaphysics； which contains the pure a priori principles of the former in their universal import） or to morals。 If we have recourse to God as the Author of all things； in order to explain the arrangements of nature or its changes； this is at least not a physical explanation； and is a complete confession that our philosophy has come to an end； since we are obliged to assume something of which in itself we have otherwise no conception； in order to be able to frame a conception of the possibility of what we see before our eyes。 Metaphysics； however； cannot enable us to attain by certain inference from the knowledge of this world to the conception of God and to the proof of His existence； for this reason； that in order to say that this world could be produced only by a God （according to the conception implied by this word） we should know this world as the most perfect whole possible； and for this purpose should also know all possible worlds （in order to be able to compare them with this）； in other words； we should be omniscient。 It is absolutely impossible； however； to know the existence of this Being from mere concepts； because every existential proposition； that is； every proposition that affirms the existence of a being of which I frame a concept； is a synthetic proposition； that is； one by which I go beyond that conception and affirm of it more than was thought in the conception itself； namely； that this concept in the understanding has an object corresponding to it outside the understanding； and this it is obviously impossible to elicit by any reasoning。 There remains； therefore； only one single process possible for reason to attain this knowledge； namely； to start from the supreme principle of its pure practical use （which in every case is directed simply to the existence of something as a consequence of reason） and thus determine its object。 Then its inevitable problem； namely； the necessary direction of the will to the summum bonum； discovers to us not only the necessity of assuming such a First Being in reference to the possibility of this good in the world； but； what is most remarkable； something which reason in its progress on the path of physical nature altogether failed to find； namely； an accurately defined conception of this First Being。 As we can know only a small part of this world； and can still less compare it with all possible worlds； we may indeed from its order； design； and greatness； infer a wise； good； powerful； etc。； Author of it； but not that He is all…wise； all…good； all…powerful； etc。 It may indeed very well be granted that we should be justified in supplying this inevitable defect by a legitimate and reasonable hypothesis； namely； that when wisdom； goodness； etc； are displayed in all the parts that offer themselves to our nearer knowledge； it is just the same in all the rest； and that it would therefore be reasonable to ascribe all possible perfections to the Author of the world； but these are not strict logical inferences in which we can pride ourselves on our insight； but only permitted conclusions in which we may be indulged and which require further recommendation before we can make use of them。 On the path of empirical inquiry then （physics）； the conception of God remains always a conception of the perfection of the First Being not accurately enough determined to be held adequate to the conception of Deity。 （With metaphysic in its transcendental part nothing whatever can be accomplished。） When I now try to test this conception by reference to the object of practical reason； I find that the moral principle admits as possible only the conception of an Author of the world possessed of the highest perfection。 He must be omniscient； in order to know my conduct up to the inmost root of my mental state in all possible cases and into all future time； omnipotent； in order to allot to it its fitting consequences； similarly He must be omnipresent； eternal； etc。 Thus the moral law； by means of the conception of the summum bonum as the object of a pure practical reason； determines the concept of the First Being as the Supreme Being； a thing which the physical （and in its higher development the metaphysical）； in other words； the whole speculative course of reason； was unable to effect。 The conception of God； then； is one that belongs originally not to physics； i。e。； to speculative reason； but to morals。 The same may be said of the other conceptions of reason of which we have treated above as postulates of it in its practical use。 In the history of Grecian philosophy we find no distinct traces of a pure rational theology earlier than Anaxagoras； but this is not because the older philosophers had not intelligence or penetration enough to raise themselves to it by the path of speculation； at least with the aid of a thoroughly reasonable hypothesis。 What could have been easier； what more natural