the fewer senses any man, as well as any other creature, hath; and the fewer and duller the impressions are that are made by them; and the duller the faculties are that are employed about them,—the more remote are they from that knowledge which is to be found in some men.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“And if a man had passed sixty years in such a state, as it is possible he might, as well as three days, I wonder what difference there would be, in any intellectual perfections, between him and the lowest degree of animals. 15. Perception the Inlet of all materials of Knowledge. Perception then being the FIRST step and degree towards knowledge, and the inlet of all the materials of it; the fewer senses any man, as well as any other creature, hath; and the fewer and duller the impressions are that are made by them; and the duller the faculties are that are employed about them,—the more remote are they from that knowledge which is to be found in some men. But this being in great variety of degrees (as may be perceived amongst men) cannot certainly be discovered in the several species of animals, much less in their particular individuals. It suffices me only to have remarked here,—that perception is the first operation of all our intellectual faculties, and the inlet of all knowledge in our minds.” source