 In space all things have spatial relations to each other, and there has to be a path of access from me to each thing. In the same way, on the basis of the concept-system, an all-comprehending conceptual space, so to speak, all concepts have relations to each other (in this case logical, conceptual relations). And here there has to be a connecting path to each concept from the contents of my experience, e.g., from my perceptions. Everything of which I can speak has to be traceable back to things experienced by me. All knowledge I can have relates either to my own feelings, mental images, thoughts, etc. or can be derived from my perceptions… 