class="pginternal" tag="{http://www.w3.org/1999/xhtml}a">What is meant by the picture being inverted  116   Cause of mistake in this matter  117   Images in the eye, not pictures of external objects  118   In what sense they are pictures  119   In this affair we must carefully distinguish between ideas of sight and touch  120   Difficult to explain by words the true Theory of Vision  121   The question, whether there is any IDEA common to sight and touch, stated  122   Abstract extension inquired into  123   It is incomprehensible  124   Abstract extension not the OBJECT of geometry  125   The general IDEA of a triangle, considered  126   Vacuum, or pure space, not common to sight and touch  127   There is no idea, or kind of idea, common to both senses  128   First argument in proof hereof  129   Second argument  130   Visible figure and extension, not distinct IDEAS from colour  131   Third argument  132   Confirmation drawn from Mr. Molyneux's problem of a sphere and a cube, published by Mr. Locke  133   Which is falsely solved, if the common supposition be true  134   More might be said in proof of our tenet, but this suffices  135   Further reflection on the foregoing problem  136   The same thing doth not affect both sight and touch  137   The same idea of motion not common to sight and touch  138   The way wherein we apprehend motion by sight, easily collected from what hath been said  139   QU. How visible and tangible IDEAS came to have the same name if not of the same kind  140   This accounted for without supposing them of the same kind  141   OBJ. That a tangible square is liker to a visible square than to a visible circle  142   ANS. That a visible square is fitter than a visible circle, to represent a tangible square  143   But it doth not hence follow, that a visible square is like a tangible square  144   Why we are more apt to confound visible with tangible IDEAS, than other signs with the things signified  145   Several other reasons hereof, assigned  146   Reluctancy in rejecting any opinion, no argument of its truth  147   Proper objects of vision the language of nature  148   In it there is much admirable, and deserving our attention  149   Question proposed, concerning the object of geometry  150   At first view we are apt to think visible extension the object of geometry  151   Visible extension shown not to be the object of geometry  152   Words may as well be thought the object of geometry, as visible extension  153   It is proposed to inquire, what progress an