V. The Activity of Knowing the World

It follows from the preceding consideration that it is impossible, through investigation of the content of our observation, to prove that our perceptions are mental pictures. This was supposedly proven by showing that if the process of perception does take place in the way one pictures it in accordance with the naive-realistic assumptions about the psychological and physiological constitution of our individuality, then we do not have to do with things-in-themselves, but merely with our mental pictures of the things. Now if naive realism consistently pursued, leads to results which represent the exact opposite of its presuppositions, then these presuppositions must be deemed unfit for founding a world view and must be dropped. In any case it is inadmissible to reject the presuppositions and to allow what follows from them to hold good, as does the critical idealist, who bases his assertion that the world is my mental picture upon the line of argument above. (Eduard von Hartmann, in his book The Basic Problem of Epistemology, gives a detailed presentation of this line of argument.