distance that the rays proceeding from A, after refraction or reflection,
be brought to unite somewhere in the AxAB. And suppose the point of union
(i.e. the image of the point A, as hath been already set forth) to be Z;
between which and B, the vertex of the glass or speculum, conceive the
eye to be anywhere placed. The question now is, where the point A ought
to appear? Experience shows that it does not appear behind at the point
Z, and it were contrary to nature that it should, since all the
impression which affects the sense comes from towards A. But from our
tenets it should seem to follow that it would appear before the eye at a
vast distance off, so great as should in some sort surpass all sensible
distance. For since if we exclude all anticipations and prejudices, every
OBJECT appears by so much the farther off, by how much the rays it sends
to the eye are less diverging. And that OBJECT is thought to be most
remote from which parallel rays proceed unto the eye. Reason would make
one think that OBJECT should appear at yet a greater distance which is
seen by converging rays. Moreover it may in general be asked concerning
this case what it is that determines the apparent place of the point A,
and maketh it to appear after a constant manner sometimes nearer, at
other times farther off? To which doubt I see nothing that can be
answered agreeable to the principles we have laid down except only that
the point A ought always to appear extremely remote. But on the contrary
we are assured by experience that the point A appears variously distant,
according to the different situations of the eye between the points B and
Z. And that it doth never (if at all) seem farther off, than it would if
it were beheld by the naked eye, but on the contrary it doth sometimes
appear much nearer. Nay, it is even certain that by how much the rays
falling on the eye do more converge by so much the nearer doth the OBJECT
seem to approach. For the eye being placed close to the point B, the
OBJECT A appears nearly in its own natural place, if the point B is taken
in the glass, or at the same distance, if in the speculum. The eye being
brought back to O, the OBJECT seems to draw near: and being come to P it
beholds it still nearer. And so on little and little, till at length the
eye being placed somewhere, suppose at Q, the OBJECT appearing extremely
near, begins to vanish into mere confusion. All which doth seem repugnant
to our principles, at le