From the foregoing considerations it follows that it is impossible to prove, by analysis of the content of our perceptions, that our percepts are ideas. This is supposed to be proved by showing that, if the process of perceiving takes place in the way in which we conceive it in accordance with the naïve-realistic assumptions concerning the psychological and physiological constitution of human individuals, then we have to do, not with things themselves, but merely with our ideas of things. Now, if Naïve Realism, when consistently thought out, leads to results which directly contradict its presuppositions, then these presuppositions must be discarded as unsuitable for the foundation of a theory of the world. In any case, it is inadmissible to reject the presuppositions and yet accept the consequences, as the Critical Idealist does who bases his assertion that the world is my idea on the line of argument indicated above. (Eduard von Hartmann gives in his work Das Grundproblem der Erkenntnistheorie a full account of this line of argument.) The truth of Critical Idealism is one thing, the persuasiveness of its proofs another. How it stands with the former, will appear later in the course of our argument, but the persuasiveness of its proofs is nil. If one builds a house, and the ground floor collapses whilst the first floor is being built, then the first floor collapses too. Naïve Realism and Critical Idealism are related to one another like the ground floor to the first floor in this simile.