[Sidenote: _Solution of other difficulties concerning the genesis of concepts._] By establishing such relations we emerge from the vicious circle, which has given such trouble to certain logicians, who have striven to explain the genesis of the concepts in terms of nominalism, but were afterwards, when probing their doctrine to the bottom, compelled to admit the _necessity of the concepts_ as a _foundation_ for the _genesis of the concepts._ They believed that they had got out of the difficulty by distinguishing two orders of concepts, primary and secondary, formative models and formations according to models; and they thus reproduced, in the semblance of a solution, the problem still unsolved. In different words, others admitted the same embarrassment. They attempted to obtain the concepts from _experience,_ but recognized at the same time that all experience presupposes an _ideal anticipation._ Or they declared that the concept fixes the _essential_ characters of things, and, at the same time, that the essential characters of things are indispensable for fixing the _concept._ Or, finally, they based the formation of concepts upon _categories,_ which, enumerated and understood as they understood them, were by no means categories and functions, but _concepts._ Primary concepts, formative models, ideal anticipations, essential concepts, concept-categories, and the like, are nothing but verbal variants of the pure concepts; the necessary presupposition, as we know, for the impure concepts or pseudoconcepts. [Sidenote: _Disputes arising from neglect of the distinction between empirical and abstract concepts._]