| 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. |
| When we are accustomed to see two impressions conjoined together, the appearance or idea of the one immediately carries us to the idea of the other. |
| Being fully satisfyed on this head, I make a third set of experiments, in order to know, whether any thing be requisite, beside the customary transition, towards the production of this phaenomenon of belief. |
| I therefore change the first impression into an idea; and observe, that though the customary transition to the correlative idea still remains, yet there is in reality no belief nor perswasion. |
| A present impression, then, is absolutely requisite to this whole operation; and when after this I compare an impression with an idea, and find that their only difference consists in their different degrees of force and vivacity, I conclude upon the whole, that belief is a more vivid and intense conception of an idea, proceeding from its relation to a present impression. |
| Thus all probable reasoning is nothing but a species of sensation. |
| It is not solely in poetry and music, we must follow our taste and sentiment, but likewise in philosophy. |
| When I am convinced of any principle, it is only an idea, which strikes more strongly upon me. |
| When I give the preference to one set of arguments above another, I do nothing but decide from my feeling concerning the superiority of their influence. |
| Objects have no discoverable connexion together; nor is it from any other principle but custom operating upon the imagination, that we can draw any inference from the appearance of one to the existence of another. |
| It will here be worth our observation, that the past experience, on which all our judgments concerning cause and effect depend, may operate on our mind in such an insensible manner as never to be taken notice of, and may even in some measure be unknown to us. |
| A person, who stops short in his journey upon meeting a river in his way, foresees the consequences of his proceeding forward; and his knowledge of these consequences is conveyed to him by past experience, which informs him of such certain conjunctions of causes and effects. |
| But can we think, that on this occasion he reflects on any past experience, and calls to remembrance instances, that he has seen or heard of, in order to discover the effects of water on animal bodies? No surely; this is not the method, in which he proceeds in his reasoning. |
| The idea of sinking is so closely connected with that of water, and the idea of suffocating with that of sinking, that the mind makes the transition without the assistance of the memory. |
| The custom operates before we have time for reflection. |
| The objects seem so inseparable, that we interpose not a moment's delay in passing from the one to the other. |
| But as this transition proceeds from experience, and not from any primary connexion betwixt the ideas, we must necessarily acknowledge, that experience may produce a belief and a judgment of causes and effects by a secret operation, and without being once thought of. |
| This removes all pretext, if there yet remains any, for asserting that the mind is convinced by reasoning of that principle, that instances of which we have no experience, must necessarily resemble those, of which we have. |