T 2.3.9.27

Thus all kinds of uncertainty have a strong connexion with fear, even tho' they do not cause any opposition of passions by the opposite views and considerations they present to us. A person, who has left his friend in any malady, will feel more anxiety upon his account, than if he were present, tho' perhaps he is not only incapable of giving him assistance, but likewise of judging of the event of his sickness. In this case, tho' the principal object of the passion, viz. the life or death of his friend, be to him equally uncertain when present as when absent; yet there are a thousand little circumstances of his friend's situation and condition, the knowledge of which fixes the idea, and prevents that fluctuation and uncertainty so near ally'd to fear. Un|certainty is, indeed, in one respect as near ally'd to hope as to fear, since it makes an essential part in the composition of the former passion; but the reason, why it inclines not to that side, is, that uncertainty alone is uneasy, and has a relation of impressions to the uneasy passions.