If it really were the case, as popular opinion has tried to establish, that the genius were separated from ordinary men by a thick wall through which no sound could penetrate, then all understanding of the efforts of genius would be denied to ordinary men, and their works would fail to make any impression on them. All hopes of progress depend on this being untrue. And it is untrue. The difference between men of genius and the others is quantitative not qualitative, of degree not of kind.

p. 121. - Sex and Character (1903)