visual angle in conjunction
with the distance. Hence, though the angle remain the same, or even
become less, yet if withal the distance seem to have been increased, the
object shall appear greater. Now, one way whereby we estimate the
distance of anything is by the number and extent of the intermediate
objects: when therefore the moon is seen in the horizon, the variety of
fields, houses, etc., together with the large prospect of the wide
extended land or sea that lies between the eye and the utmost limb of the
horizon, suggest unto the mind the idea of greater distance, and
consequently magnify the appearance. And this, according to Dr. Wallis,
is the true account of the extraordinary largeness attributed by the mind
to the horizontal moon at a time when the angle subtended by its diameter
is not one jot greater than it used to be.

77. With reference to this opinion, not to repeat what hath been already
said concerning distance, I shall only observe, FIRST, that if the
prospect of interjacent objects be that which suggests the idea of
farther distance, and this idea of farther distance be the cause that
brings into the mind the idea of greater magnitude, it should hence
follow that if one looked at the horizontal moon from behind a wall, it
would appear no bigger than ordinary. For in that case the wall
interposing cuts off all that prospect of sea and land, etc. which might
otherwise increase the apparent distance, and thereby the apparent
magnitude of the moon. Nor will it suffice to say the memory doth even
then suggest all that extent of land, etc., which lies within the
horizon; which suggestion occasions a sudden judgment of sense that the
moon is farther off and larger than usual. For ask any man who, from such
a station beholding the horizontal moon, shall think her greater than
usual, whether he hath at that time in his mind any idea of the
intermediate objects, or long tract of land that lies between his eye and
the extreme edge of the horizon? And whether it be that idea which is the
cause of his making the aforementioned judgment? He will, I suppose,
reply in the negative, and declare the horizontal moon shall appear
greater than the meridional, though he never thinks of all or any of
those things that lie between him and it. SECONDLY, it seems impossible
by this hypothesis to account for the moon's appearing in the very same
situation at one time greater than at another; which nevertheless has
been shown