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313 Nothing is more fluctuating and inconstant on many occasions, than the will of man; nor is there any thing but strong motives, which can give us an absolute certainty in pronouncing concerning any of his future actions. When we see a person free from these motives, we suppose a possibility either of his acting or forbearing; and tho' in general we may conclude him to be determin'd by motives and causes, yet this removes not the uncertainty of our judgment concerning these causes, nor the influence of that uncertainty on the passions. Since therefore we ascribe a power of performing an action to every one, who has no very powerful motive to forbear it, and refuse it to such as have; it may justly be concluded, that power has always a reference to its exercise, either actual or probable, and that we consider a person as endow'd with any ability when we find from past experience, that 'tis probable, or at least possible he may exert it. And indeed, as our passions always regard the real existence of objects, and we always judge of this reality from past instances; nothing can be more likely of itself, without any farther reasoning, than that power consists in the possibility or probability of any action, as discover'd by experience and the practice of the world.

Now 'tis evident, that wherever a person is in such a situation with regard to me, that there is no very powerful motive to deter him from injuring me, and consequently 'tis uncertain whether he will injure me or not, I must be uneasy in such a situation, and cannot consider the possibility or probability of that injury without a sensible concern. The passions are not only affected by such events as are certain and infallible, but also in an inferior degree by such as are possible and contingent. And tho' perhaps I never really feel any harm, and discover by the event, that, philosophically speaking, the person never had any power of harming me; since he did not exert any; this prevents not my uneasiness from the preceding uncertainty. The agreeable passions may here operate as well as the uneasy, and convey a