conjunction of objects, it must arrive at its perfection by
degrees, and must acquire new force from each instance, that falls under
our observation. The first instance has little or no force: The second
makes some addition to it: The third becomes still more sensible; and it
is by these slow steps, that our judgment arrives at a full assurance.
But before it attains this pitch of perfection, it passes through
several inferior degrees, and in all of them is only to be esteemed a
presumption or probability. The gradation, therefore, from probabilities
to proofs is in many cases insensible; and the difference betwixt these
kinds of evidence is more easily perceived in the remote degrees, than
in the near and contiguous.

It is worthy of remark on this occasion, that though the species of
probability here explained be the first in order, and naturally takes
place before any entire proof can exist, yet no one, who is arrived at
the age of maturity, can any longer be acquainted with it. It is true,
nothing is more common than for people of the most advanced knowledge
to have attained only an imperfect experience of many particular events;
which naturally produces only an imperfect habit and transition: But
then we must consider, that the mind, having formed another observation
concerning the connexion of causes and effects, gives new force to
its reasoning from that observation; and by means of it can build an
argument on one single experiment, when duly prepared and examined. What
we have found once to follow from any object, we conclude will for ever
follow from it; and if this maxim be not always built upon as certain,
it is not for want of a sufficient number of experiments, but because
we frequently meet with instances to the contrary; which leads us to
the second species of probability, where there is a contrariety in our
experience and observation.

It would be very happy for men in the conduct of their lives and
actions, were the same objects always conjoined together, and, we had
nothing to fear but the mistakes of our own judgment, without having any
reason to apprehend the uncertainty of nature. But as it is frequently
found, that one observation is contrary to another, and that causes and
effects follow not in the same order, of which we have I had experience,
we are obliged to vary our reasoning on, account of this uncertainty,
and take into consideration the contrariety of events. The first
question, that occ