Apparent magnitude of a line is not simply as the optique angle, but directly as the optique angle, & reciprocally as the confusion, &c. (i.e. the other sensations, or want of sensation, that attend near vision). Hence great mistakes in assigning the magnifying power of glasses. Vid. Moly[neux], p. 182. Glasses or speculums may perhaps magnify or lessen without altering the optique angle, but to no purpose. Qu. Whether purblind would think objects so much diminished by a convex speculum as another? ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Qu. Wherein consists identity of person? Not in actual consciousness; for then I’m not the same person I was this day twelvemonth but while I think of wt I then did. Not in potential; for then all persons may be the same, for ought we know. Mem. Story of Mr. Deering’s aunt. Two sorts of potential consciousness—natural & præternatural. In the last § but one, I mean the latter. ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ If by magnitude be meant the proportion anything bears to a determined tangible extension, as inch, foot, &c., this, ’tis plain, cannot be properly & _per se_ perceived by sight; & as for determin’d visible inches, feet, &c., there can be no such thing obtain’d by the meer act of seeing—abstracted from experience, &c. The greatness _per se_ perceivable by the sight is onely the proportion any visible appearance bears to the others seen at the same time; or (which is the same thing) the proportion of any particular part of the visual orb to the whole. But mark that we perceive not it is an orb, any more than a plain, but by reasoning. This is all the greatness the pictures have _per se_. Hereby meere seeing cannot at all judge of the extension of any object, it not availing to know the object makes such a part of a sphærical surface except we also know the greatness of the sphærical surface; for a point may subtend the same angle wth a mile, & so create as great an image in the retina, i.e. take up as much of the orb. Men judge of magnitude by faintness and vigorousness, by distinctness and confusion, with some other circumstances, by great & little angles. Hence ’tis plain the ideas of sight which are now connected with greatness might have been connected wth smallness, and vice versâ: there being no necessary reason why great angles, faintness, and distinctness without straining, should stand for great extension, any more than a great angle, vigorousness, and confusion(227). My end is not to deliver metaphysiques altogether in a general scholastic way, but in some measure to accommodate them to the sciences, and shew how they may be useful in optiques, geometry, &c.(228) Qu. Whether _per se_ proportion of visible magnitudes be perceivable by sight? This is put on account of distinctness and confusedness, the act of perception seeming to be as great in viewing any point of the visual orb distinctly, as in viewing the whole confusedly.