Since all reasonings concerning facts or causes is
derived merely from custom, it may be asked how it happens,
that men so much surpass animals in reasoning, and one man
so much surpasses another? Has not the same custom the same
influence on all?
We shall here endeavour briefly to explain the great difference in human understandings: After which the reason of the difference between men and animals will easily be comprehended.
When we have lived any time, and have been accustomed to
the uniformity of nature, we acquire a general habit, by
which we always transfer the known to the unknown, and
conceive the latter to resemble the former. By means of this
general habitual principle, we regard even one experiment as
the foundation of reasoning, and expect a similar event with
some degree of certainty, where the experiment has been made
accurately, and free from all foreign circumstances. It is
therefore considered as a matter of great importance to
observe the consequences of things; and as one man may very
much surpass another in attention and memory and
observation, this will make a very great difference in their
reasoning.
Where there is a complication of causes to produce any
effect, one mind may be much larger than another, and better
able to comprehend the whole system of objects, and to infer
justly their consequences.
One man is able to carry on a chain of consequences to a
greater length than another.
Few men can think long without running into a confusion
of ideas, and mistaking one for another and there are
various degrees of this infirmity.
The circumstance, on which the effect depends, is
frequently involved in other circumstances, which are
foreign and extrinsic. The separation of it often requires
great attention, accuracy, and subtilty.
The forming of general maxims from particular observation
is a very nice operation; and nothing is more usual, from
haste or a narrowness of mind, which sees not on all sides,
than to commit mistakes in this particular.
When we reason from analogies, the man, who has the
greater experience or the greater promptitude of suggesting
analogies, will be the better reasoner.
Biases from prejudice, education, passion, party, etc.
hang more upon one mind than another.
After we have acquired a confidence in human testimony,
books and conversation enlarge much more the sphere of one
man's experience and thought than those of another.
It would be easy to discover many other circumstances that
make a difference in the understandings of men.