T 2.2.9.2

In order to cause a transition of passions, there is requir'd a double relation of impressions and ideas, nor is one relation sufficient to produce this effect. But that we may understand the full force of this double relation, we must consider, that 'tis not the present sensation alone or momentary pain or pleasure, which determines the character of any passion, but the whole bent or tendency of it from the beginning to the end. One impression may be related to another, not only when their sensations are resembling, as we have all along suppos'd in the preceding cases; but also when their impulses or directions are similar and correspondent. This cannot take place with regard to pride and |humility; because these are only pure sensations, without any direction or tendency to action. We are, therefore, to look for instances of this peculiar relation of impressions only in such affections, as are attended with a certain appetite or desire; such as those of love and hatred.