of his senses, is competent to form ideas of the universe, is to assert,
that a blind man is in a capacity to form a true idea of a picture, that
represents some fact of which he has never heard any one speak.

It is very easy to perceive the source of those errors, into which men,
otherwise extremely profound and very enlightened have fallen, when they
have been desirous to speak of the soul: to describe its operations.
Obliged either by their own prejudices, or by the fear of combatting the
opinions of some imperious theologian, they have become the advocates of
the principle, that the soul was a pure spirit: an immaterial substance;
of an essence directly different from that of the body; from every thing
we behold: this granted, they have been incompetent to conceive how
material objects could operate, in what manner gross and corporeal
organs were enabled to act on a substance, that had no kind of analogy
with them; how they were in a capacity to modify it by conveying its
ideas; in the impossibility of explaining this phenomenon, at the same
time perceiving that the soul had ideas, they concluded that it must
draw them from itself, and not from those beings, which according to
their own hypothesis, were incapable of acting on it, or rather, of
which they could not conceive the manner of action; they therefore
imagined that all the modifications, all the actions of this soul,
sprung from its own peculiar energy, were imprinted on it from its first
formation, by the Author of Nature: that these did not in any manner
depend upon the beings of which we have a knowledge, or which act upon
it, by the gross means of our senses.

There are, however, some phenomena, which, considered superficially,
appear to support the opinion of these philosophers; to announce a
faculty in the human soul of producing ideas within itself, without any
exterior aid; these are _dreams_, in which the interior organ of man,