IV. The fourth limitation is derived from the inconstancy of the cause of these passions, and from the short duration of its connexion with ourselves. What is casual and inconstant gives but little joy, and less pride. We are not much satisfied with the thing itself; and are still less apt to feel any new degrees of self-satisfaction upon its account. We foresee and anticipate its change by the imagination, which makes us little satisfied with the thing: we compare it to ourselves, whose existence is more durable, by which means its inconstancy appears still greater. It seems ridiculous to infer an excellency in ourselves from an object which is of so much shorter duration, and attends us during so small a part of our existence. 'Twill be easy to comprehend the reason why this cause operates not with the same force in joy as in pride; since the idea of self is not so essential to the former passion as to the latter. V. I may add, as a fifth limitation, or rather enlargement of this system, that _general rules_ have a great influence upon pride and humility, as well as on all the other passions. Hence we form a notion of different ranks of men, suitable to the power or riches they are possessed of; and this notion we change not upon account of any peculiarities of the health or temper of the persons, which may deprive them of all enjoyment in their possessions. This may be accounted for from the same principles that explained the influence of general rules on the understanding. Custom readily carries us beyond the just bounds in our passions as well as in our reasonings.