The second and the third arguments busy themselves to show that there are unmistakable differences between ideas which have their origin in the "brisk acting" of objects without and ideas of memory or imagination. The two classes are shown to be distinct, and it is very properly held that ideas of different kinds should not be confounded. But the statement, that ideas may be divided into two classes, is a very different one from the statement that the two classes differ in that one has external correlates and the other has not. One may admit all the distinctions which Locke makes in the field of ideas; and, it being once proved that such distinctions imply a world of "real" things in relation to certain ideas, may grant very readily that these ideas have corresponding to them "real" things, or that ideas caused by "real" things differ by such and such marks from other ideas. But, until it be proved that the marks in question do give a right to infer "real" things, it should not be assumed that any given class of ideas is caused by "real" things. What is to be discovered is assumed. And it is assumed here, as above, because Locke could not keep distinct the two classes of things. He is capable of saying, "But if I turn my eyes at noon towards the sun, I cannot avoid the ideas which the light, or sun, then produces in me," when the whole dispute is over the question whether there be a "real" sun toward which "real" eyes may be turned. How does he know that he is turning his eyes toward the sun? Does he not see it up there? Is he not "actually looking upon it?" His error is too plain to overlook. But if one could doubt his confusion of the two suns, the apparent and the "real," his illustration from the diagrams used in mathematical demonstration would lay the doubt once for all. "Real" lines exist, "for it would be very strange that a man should allow it for an undeniable truth, that two angles of a figure, which he measures by lines and angles of a diagram, should be bigger one than the other; and yet doubt of the existence of those lines and angles, which by looking on he makes use of to measure that by." The English is not as bad as the reasoning.