I find, that an impression, from which, on its first appearance, I can draw no conclusion, may afterwards become the foundation of belief, when I have had experience of its usual consequences.

We must in every case have observed the same impression in past instances, and have found it to be constantly conjoined with some other impression.

This is confirmed by such a multitude of experiments, that it admits not of the smallest doubt.
From a second observation I conclude, that the belief, which attends the present impression, and is produced by a number of past impressions and conjunctions; that this belief, I say, arises immediately, without any new operation of the reason or imagination.

Of this I can be certain, because I never am conscious of any such operation, and find nothing in the subject, on which it can be founded.

Now as we call every thing CUSTOM, which proceeds from a past repetition, without any new reasoning or conclusion, we-may establish it as a certain truth, that all the belief, which follows upon any present impression, is derived solely from that origin.