" I cannot in any case agree with Keiss that my whole conception of the external world has been derived from perceptions.

The most fundamental idea, the idea of existence, has not been received by me through sensation; indeed, there is no special sense-organ for the transmission of such an idea.

" "Yes, but they--Wurt, and Knaust, and Pripasov--would answer that your consciousness of existence is derived from the conjunction of all your sensations, that that consciousness of existence is the result of your sensations.

Wurt, indeed, says plainly that, assuming there are no sensations, it follows that there is no idea of existence.