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In order to carry on physiology in good conscience, people must hold to the principle that the sense organs are not phenomena in the sense of idealistic philosophy: as such they could not, in fact, be causes! And so sensualism at least as a regulative hypothesis, if not as a heuristic principle.- What's that? And other people even say that the outer world might be the work of our organs? But then our bodies, as a part of this outer world, would, in fact, be the work of our organs! But then our organs themselves would, in fact, be - the work of our organs. It seems to me that this is a fundamental reductio ad absurdum [absurd conclusion] provided that the idea of causa sui [something being its own cause] is fundamentally absurd. Consequently, is the exterior world not the work of our organs -?