without this motion of the eye, this turning it up and down in order to discern different objects, doubtless erect, inverse, and other the like terms relating to the position of tangible objects, would never have been transferred, or in any degree apprehended to belong to the ideas of sight:  the mere act of seeing including nothing in it to that purpose; whereas the different situations of the eye naturally direct the mind to make a suitable judgment of the situation of objects intromitted by it.

99.  Farther, when he has by experience learned the connexion there is between the several ideas of sight and touch, he will be able, by the perception he has of the situation of visible things in respect of one another, to make a sudden and true estimate of the situation of outward, tangible things corresponding to them.  And thus it is he shall perceive by sight the situation of external objects which do not properly fall under that sense.

100.  I know we are very prone to think that, if just made to see, we should judge of the situation of visible things as we do now:  but we are also as prone to think that, at first sight, we should in the same way apprehend the distance and magnitude of objects as we do now:  which hath been shown to be a false and groundless persuasion.  And for the like reasons the same censure may be passed on the positive assurance that most men, before they have thought sufficiently of the matter, might have of their being able to determine by the eye at first view, whether objects were erect or inverse.

101.  It will, perhaps, be objected co our opinion that a man, for instance, being thought erect when his feet are next the earth, and inverted when his head is next the earth, it doth hence follow that by the mere act of vision, without any experience or altering the situation of the eye, we should have determined whether he were erect or inverted:  for both the earth itself, and the limbs of the man who stands thereon, being equally perceived by sight, one cannot choose seeing what part of the man is nearest the earth, and what part farthest from it, i.e. whether he be erect or inverted.

I02.  To which I answer, the ideas which constitute the tangible earth and man are entirely different from those which constitute the visible earth and man.  Nor was it possible, by virtue of the visive faculty alone, without superadding any experience of touch, or altering the position of the eye, ever to have known, or so much as suspected, there had been any relation or connexion between them.  Hence a man at first view would not denominate anything he saw earth, or head, or foot; and consequently he could not tell by the mere act of vision whether the head or feet were nearest the earth:  nor, indeed, would we have thereby any thought of earth or man, erect or inverse, at all:  which will be made yet more evident if we nicely observe, and make a particular comparison between, the ideas of both senses.