The idea is the adequate concept, the objectively true, or the true as such. If anything has truth, it has it by virtue of its idea, or something has truth only in so far as it is idea. – The expression “idea” has otherwise also often been used in philosophy as well as in ordinary life for “concept,” or even for just a “representation.” To say that I still have no idea of this lawsuit, this building, this region, means nothing more than I still have no representation of it. It is Kant who reclaimed the expression “idea” for the “concept of reason.” – Now according to Kant the concept of reason should be the concept of the unconditional, but a concept which is transcendent with respect to appearances, that is, one for which no adequate empirical use can be made. The concepts of reason are supposed to serve for the comprehension of perceptions, those of the understanding for the understanding of them. – In fact, however, if these last concepts of the understanding are truly concepts, then they are comprehensions, which means concepts; they will make comprehending5 possible, and an understanding of perceptions through concepts of the understanding will be a comprehending. But if understanding is only the determining of perceptions by categories such as whole and parts, force, cause, and the like, then it signifies only a determining by means of reflection, just as by understanding one may mean only the determinate representation of a fully determined sensuous content; as when someone is being shown the way, that at the end of the wood he must turn left, and he replies “I understand,” understanding means nothing more than a grasp in pictorial representation and in memory. – “Concept of reason,” too, is a somewhat clumsy expression; for the concept is in general something rational, and in so far as reason is distinguished from the understanding and the concept as such, it is the totality of the concept and objectivity. – The idea is the rational in this sense; it is the unconditioned, because only that has conditions which essentially refers to an objectivity that it does not determine itself but which still stands over against it in the form of indifference and externality, just as the external purpose had conditions.