Evils that are certain have sometimes the same effect in producing fear, as the possible or impossible. Thus, a man in a strong prison well-guarded, without the least means of escape, trembles at the thought of the rack, to which he is sentenced. This happens only when the certain evil is terrible and confounding; in which case the mind continually rejects it with horror, while it continually presses in upon the thought. The evil is there fixed and established, but the mind cannot endure to fix upon it; from which fluctuation and uncertainty there arises a passion of much the same appearance with fear.
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 killed, 'tis evident the passion this event would occasion, would 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 though 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.
From these principles we may account for a phenomenon in the passions, which at first sight seems very extraordinary, viz. that surprise is apt to change into fear, and every thing that is unexpected affrights us. The most obvious conclusion from this is, that human nature is in general pusillanimous; since, upon the sudden appearance of any object, we immediately conclude it to be an evil, and, without waiting till we can examine its nature, whether it be good or bad, are at first affected with fear. This, I say, is the most obvious conclusion; but upon farther examination, we shall find that the phenomenon is otherwise to be accounted for. The suddenness and strangeness of an appearance naturally excite a commotion in the mind, like every thing for which we are not prepared, and to which we are not accustomed. This commotion, again, naturally produces a curiosity or inquisitiveness, which, being very violent, from the strong and sudden impulse of the object, becomes uneasy, and resembles in its fluctuation and uncertainty, the sensation of fear, or the mixed passions of grief and joy. This image of fear naturally converts into the thing itself, and gives us a real apprehension of evil, as the mind always forms its judgments more from its present disposition than from the nature of its objects.
Thus all kinds of uncertainty have a strong connexion with fear, even though 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, though perhaps he is not only incapable of giving him assistance, but likewise of judging of the event of his sickness. In this case, though the principle 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 nearly allied to fear. Uncertainty is, indeed, in one respect, as nearly allied 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.
'Tis thus our uncertainty concerning any minute circumstance relating to a person, increases our apprehensions of his death or misfortune. Horace has remarked this phenomenon:
Ut assidens implumibus pullus avis
Serpentium allapsus timet,
Magis relictis; non, ut adsit, auxili
Latura plus presentibus.
But this principle of the connexion of fear with uncertainty I carry farther, and observe, that any doubt produces that passion, even though it presents nothing to us on any side but what is good and desirable. A virgin, on her bridal-night goes to bed full of fears and apprehensions, though she expects nothing but pleasure of the highest kind, and what she has long wished for. The newness and greatness of the event, the confusion of wishes and joys, so embarrass the mind, that it knows not on what passion to fix itself; from whence arises a fluttering or unsettledness of the spirits, which being, in some degree, uneasy, very naturally degenerates into fear.
Thus we still find, that whatever causes any fluctuation or mixture of passions, with any degree of uneasiness, always produces fear, or at least a passion so like it, that they are scarcely to be distinguished.
I have here confined myself to the examination of hope and fear in their most simple and natural situation, without considering all the variations they may receive from the mixture of different views and reflections. Terror, consternation, astonishment, anxiety, and other passions of that kind, are nothing but different species and degrees of fear. 'Tis easy to imagine how a different situation of the object, or a different turn of thought, may change even the sensation of a passion; and this may in general account for all the particular subdivisions of the other affections, as well as of fear. Love may show itself in the shape of tenderness, friendship, intimacy, esteem, good-will, and in many other appearances; which at the bottom are the same affections, and arise from the same causes, though with a small variation, which it is not necessary to give any particular account of. 'Tis for this reason I have all along confined myself to the principal passion.