T 2.3.9.26

From these principles we may account for a phænomenon in the passions, which at first sight seems very extraordinary, viz. that surprize 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 pusilanimous; 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 phænomenon 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 prepar'd, and to which we are not accustom'd. 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 mix'd 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.