 You believe this floor exists because you feel it resist you…. But do you think your ideas do not resist you? Find me then two unequal diameters in a circle, or three equal ones in an ellipse. Find me the square root of eight and the cube root of nine…. [M]ake two feet of intelligible extension equal no more than one. Certainly the nature of this extension cannot countenance that. It resists your mind. Do not, therefore, doubt its reality. (ibid., OC 12:41–2; JS:13–14)