not imaginable seems to them not intelligible. The truth of this is
sufficiently manifest from the single circumstance, that the philosophers
of the schools accept as a maxim that there is nothing in the
understanding which was not previously in the senses, in which however it
is certain that the ideas of God and of the soul have never been; and it
appears to me that they who make use of their imagination to comprehend
these ideas do exactly the some thing as if, in order to hear sounds or
smell odors, they strove to avail themselves of their eyes; unless indeed
that there is this difference, that the sense of sight does not afford us
an inferior assurance to those of smell or hearing; in place of which,
neither our imagination nor our senses can give us assurance of anything
unless our understanding intervene.

Finally, if there be still persons who are not sufficiently persuaded of
the existence of God and of the soul, by the reasons I have adduced, I am
desirous that they should know that all the other propositions, of the
truth of which they deem themselves perhaps more assured, as that we have
a body, and that there exist stars and an earth, and such like, are less
certain; for, although we have a moral assurance of these things, which is
so strong that there is an appearance of extravagance in doubting of their
existence, yet at the same time no one, unless his intellect is impaired,
can deny, when the question relates to a metaphysical certitude, that
there is sufficient reason to exclude entire assurance, in the observation
that when asleep we can in the same way imagine ourselves possessed of
another body and that we see other stars and another earth, when there is
nothing of the kind. For how do we know that the thoughts which occur in
dreaming are false rather than those other which we experience when awake,
since the former are often not less vivid and distinct than the latter?
And though men of the highest genius study this question as long as they
please, I do not believe that they will be able to give any reason which