Nothing is so convenient as a decisive argument of this kind, which
must at least _silence_ the most arrogant bigotry and superstition, and
free us from their impertinent solicitations. I flatter myself, that I
have discovered an argument of a like nature, which, if just, will, with
the wise and learned, be an everlasting check to all kinds of
superstitious delusion, and consequently, will be useful as long as the
world endures. For so long, I presume, will the accounts of miracles and
prodigies be found in all history, sacred and profane.
87. Though experience be our only guide in reasoning concerning matters
of fact; it must be acknowledged, that this guide is not altogether
infallible, but in some cases is apt to lead us into errors. One, who in
our climate, should expect better weather in any week of June than in
one of December, would reason justly, and conformably to experience; but
it is certain, that he may happen, in the event, to find himself
mistaken. However, we may observe, that, in such a case, he would have
no cause to complain of experience; because it commonly informs us
beforehand of the uncertainty, by that contrariety of events, which we
may learn from a diligent observation. All effects follow not with like
certainty from their supposed causes. Some events are found, in all
countries and all ages, to have been constantly conjoined together:
Others are found to have been more variable, and sometimes to disappoint
our expectations; so that, in our reasonings concerning matter of fact,
there are all imaginable degrees of assurance, from the highest
certainty to the lowest species of moral evidence.
A wise man, therefore, proportions his belief to the evidence. In such
conclusions as are founded on an infallible experience, he expects the
event with the last degree of assurance, and regards his past experience
as a full _proof_ of the future existence of that event. In other
cases, he proceeds with more caution: He weighs the opposite
experiments: He considers which side is supported by the greater number
of experiments: to that side he inclines, with doubt and hesitation; and
when at last he fixes his judgement, the evidence exceeds not what we
properly call _probability_. All probability, then, supposes an
opposition of experiments and observations, where the one side is found
to overbalance the other, and to produce a degree of evidence,
proportioned to the superiority. A hundred instances or experiments on
one side, and fifty on another, afford a doubtful expectation of any
event; though a hundred uniform experiments, with only one that is
contradictory, reasonably beget a pretty strong degree of assurance. In
all cases, we must balance the opposite experiments, where they are
opposite, and deduct the smaller number from the greater, in order to
know the exact force of the superior evidence.