'Tis after this manner that hope and fear arise from the different mixture of these opposite passions of grief and joy, and from their imperfect union and conjunction.
Upon the whole, contrary passions succeed each other alternately, when they arise from different objects: They mutually destroy each other, when they proceed from different parts of the same: And they subsist both of them, and mingle together, when they are deriv'd from the contrary and incompatible chances or possibilities, on which any one object depends. The influence of the relations of ideas is plainly seen in this whole affair. If the objects of the contrary passions be totally different, the passions are like two opposite liquors in different bottles, which have no influence on each other. If the objects be intimately connected, the passions are like an alcali and an acid, which, being mingled, destroy each other. If the relation be more imperfect, and consists in the contradictory views of the same object, the passions are like oil and vinegar, which, however mingled, never perfectly unite and incorporate.
As the hypothesis concerning hope and fear carries its own evidence along with it, we shall be the more concise in our proofs. A few strong arguments are better than many weak ones.
The passions of fear and hope may arise when the chances are equal on both sides, and no superiority can be discover'd in the one above the other. Nay, in this situation the passions are rather the strongest, as the mind has then the least foundation to rest upon, and is toss'd with the greatest uncertainty. Throw in a superior degree of probability to the side of grief you immediately see that passion diffuse itself over the composition, and tincture it into fear. Encrease the probability, and by that means the grief, the fear prevails still more and more, till at last it runs insensibly, as the joy continually diminishes, into pure grief, after you have brought it to this situation, diminish the grief, after the same manner that you encreas'd it; by diminishing the probability
