T 2.3.10.7

But beside the action of the mind, which is the principal foundation of the pleasure, there is likewise requir'd a degree of success in the attainment of the end, or the discovery of that truth we examine. Upon this head I shall make a general remark, which may be useful on many occasions, viz. that where the mind pursues any end with passion; tho' that passion be not deriv'd originally from the end, but merely from the action and pursuit; yet by the natural course of the affections, we acquire a concern for the end itself, and are uneasy under any disappointment we meet with in the pursuit of it. This proceeds from the relation and parallel direction of the passions above-mention'd.