T 2.3.9.25

But 'tis not only where good or evil is uncertain, as to its existence, but also as to its kind, that fear or hope arises. Let one be told by a person, whose veracity he cannot doubt of, that one of his sons is suddenly kill'd, 'tis evident the passion this event wou'd occasion, wou'd not settle into pure grief, till he got certain information, which of his sons he had lost. Here there is an evil certain, but the kind of it uncertain: Consequently the fear we feel on this occasion is without the least mixture of joy, and arises merely from the fluctuation of the fancy betwixt its objects. And tho' each side of the question produces here the same passion, yet that passion cannot settle, but receives from the imagination a tremulous and unsteady motion, resembling in its cause, as well as in its sensation, the mixture and contention of grief and joy.