Know that for the human mind there are certain objects of perception
which are within the scope of its nature and capacity; on the other
hand, there are, amongst things which actually exist, certain objects
which the mind can in no way and by no means grasp: the gates of
perception are closed against it. Further, there are things of which
the mind understands one part, but remains ignorant of the other; and
when man is able to comprehend certain things, it does not follow that
he must be able to comprehend everything. This also applies to the
senses: they are able to perceive things, but not at every distance;
and all other powers of the body are limited in a similar way. A man
can, e.g., carry two kikkar, but he cannot carry ten kikkar. How
individuals of the same species surpass each other in these sensations
and in other bodily faculties is universally known, but there is a
limit to them, and their power cannot extend to every distance or to
every degree.
All this is applicable to the intellectual faculties of man. There is a
considerable difference between one person and another as regards these
faculties, as is well known to philosophers. While one man can discover
a certain thing by himself, another is never able to understand it,
even if taught by means of all possible expressions and metaphors, and
during a long period; his mind can in no way grasp it, his capacity is
insufficient for it. This distinction is not unlimited. A boundary is
undoubtedly set to the human mind which it cannot pass. There are
things (beyond that boundary) which are acknowledged to be inaccessible
to human understanding, and man does not show any desire to comprehend
them, being aware that such knowledge is impossible, and that there are
no means of overcoming the difficulty; e.g., we do not know the number
of stars in heaven, whether the number is even or odd; we do not know
the number of animals, minerals, or plants, and the like. There are
other things, however, which man very much desires to know, and
strenuous efforts to examine and to investigate them have been made by
thinkers of all classes, and at all times. They differ and disagree,
and constantly raise new doubts with regard to them, because their
minds are bent on comprehending such things, that is to say, they are
moved by desire; and every one of them believes that he has discovered
the way leading to a true knowledge of the thing, although human reason
is entirely unable to demonstrate the fact by convincing evidence.—For
a proposition which can be proved by evidence is not subject to
dispute, denial, or rejection; none but the ignorant would contradict
it, and such contradiction is called “denial of a demonstrated proof.”
Thus you find men who deny the spherical form of the earth, or the
circular form of the line in which the stars move, and the like; such
men are not considered in this treatise. This confusion prevails mostly
in metaphysical subjects, less in problems relating to physics, and is
entirely absent from the exact sciences. Alexander Aphrodisius said
that there are three causes which prevent men from discovering the
exact truth: first, arrogance and vainglory; secondly, the subtlety,
depth, and difficulty of any subject which is being examined; thirdly,
ignorance and want of capacity to comprehend what might be
comprehended. These causes are enumerated by Alexander. At the present
time there is a fourth cause not mentioned by him, because it did not
then prevail, namely, habit and training. We naturally like what we
have been accustomed to, and are attracted towards it. This may be
observed amongst villagers; though they rarely enjoy the benefit of a
douche or bath, and have few enjoyments, and pass a life of privation,
they dislike town life and do not desire its pleasures, preferring the
inferior things to which they are accustomed, to the better things to
which they are strangers; it would give them no satisfaction to live in
palaces, to be clothed in silk, and to indulge in baths, ointments, and
perfumes.
The same is the case with those opinions of man to which he has been
accustomed from his youth; he likes them, defends them, and shuns the
opposite views. This is likewise one of the causes which prevent men
from finding truth, and which make them cling to their habitual
opinions. Such is, e.g., the case with the vulgar notions with respect
to the corporeality of God, and many other metaphysical questions, as
we shall explain. It is the result of long familiarity with passages of
the Bible, which they are accustomed to respect and to receive as true,
and the literal sense of which implies the corporeality of God and
other false notions; in truth, however, these words were employed as
figures and metaphors for reasons to be mentioned below. Do not imagine
that what we have said of the insufficiency of our understanding and of
its limited extent is an assertion founded only on the Bible; for
philosophers likewise assert the same, and perfectly understand it,
without having regard to any religion or opinion. It is a fact which is
only doubted by those who ignore things fully proved. This chapter is
intended as an introduction to the next.