In the foregoing part of this chapter, it is suggested, that some circumstances make beings or things fit objects for desire, others not. This hint must be pursued. It is a truth ascertained by universal experience, that a thing which in our apprehension is beyond reach, never is the object of desire. No man, in his right senses, desires to walk in the air, or to descend to the centre of the earth. We may amuse ourselves in a reverie, with building castles in the air, and wishing for what can never happen. But such things never move desire. And indeed a desire to act would be altogether absurd, when we are conscious that the action is beyond our power. In the next place, though the difficulty of attainment with respect to things within reach, often inflames desire; yet where the prospect of attainment is faint and the event extremely uncertain, the object, however agreeable, seldom raiseth any strong desire. Thus beauty or other good qualities in a woman of rank, seldom raises love in any man greatly her inferior. In the third place, different objects, equally within reach, raise emotions in different degrees; and when desire accompanies any of these emotions, its strength, as is natural, is proportioned to that of its cause. Hence the remarkable difference among desires directed upon beings inanimate, animate, and rational. The emotion caused by a rational being, is out of measure stronger than any caused by an animal without reason; and an emotion raised by such an animal, is stronger than what is caused by any thing inanimate. There is a separate reason why desire of which a rational being is the object should be the strongest. Desire directed upon such a being, is gratified many ways, by loving, serving, benefiting, the object; and it is a well known truth, that our desires naturally swell by exercise. Desire directed upon an inanimate being, susceptible neither of pleasure nor pain, is not capable of a higher gratification than that of acquiring the property. Hence it is, that though every feeling which raiseth desire, is strictly speaking a passion; yet commonly those feelings only are denominated passions of which sensible beings capable of pleasure and pain are the objects. SECT. II. _Causes of the emotions of joy and sorrow._