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 satisfyed 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 satisfyed 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. It will 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 of riches they are possest 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. It may not be amiss to observe on this occasion, that the influence of general rules and maxims on the passions very much contributes to facilitate the effects of all the principles, which we shall explain in the progress of this treatise. For it is evident, that if a person full-grown, and of the same nature with ourselves, were on a sudden-transported into our world, he would be very much embarrased with every object, and would not readily find what degree of love or hatred, pride or humility, or any other passion he ought to attribute to it. The passions are often varyed by very inconsiderable principles; and these do not always play with a perfect regularity, especially on the first trial. But as custom and practice have brought to light all these principles, and have settled the just value of every thing; this must certainly contribute to the easy production of the passions, and guide us, by means of general established maxims, in the proportions we ought to observe in preferring one object to another. This remark may, perhaps, serve to obviate difficulties, that mayarise concerning some causes, which I shall hereafter ascribe to particular passions, and which may be esteemed too refined to operate so universally and certainly, as they are found to do.