When emotions and passions are felt thus by intervals and have not a continued existence, it may be thought a nice problem, to ascertain their identity, and to determine when they are the same when different. In a strict philosophic view, every single impression made even by the same object, is distinguishable from what have gone before, and from what succeed. Neither is an emotion raised by an idea the same with what is raised by a sight of the object. But such accuracy is not found in common apprehension, nor is necessary in common language. The emotions raised by a fine landscape in its successive appearances, are not distinguished from each other, nor even from those raised by successive ideas of the object: all of them are held to be the same. A passion also is always reckoned the same, so long as it is fixed upon the same object. Thus love and hatred may continue the same for life. Nay, so loose are we in this way of thinking, that many passions are reckoned the same even after a change of object. This is the case of all passions that proceed from some peculiar propensity. Envy, for example, is considered to be the same passion, not only while it is directed upon the same person, but even where it comprehends many persons at once. Pride and malice are in the same condition. So much was necessary to be said upon the identity of a passion and emotion, in order to prepare for examining their growth and decay. The growth and decay of passions and emotions, is a subject too extensive to be exhausted in an undertaking like the present. I pretend only to give a cursory view of it, so far as necessary for the purposes of criticism. Some emotions are produced in their utmost perfection, and have a very short endurance. This is the case of surprise, of wonder, and sometimes of terror. Emotions raised by insensible objects, such as trees, rivers, buildings, pictures, arrive at perfection almost instantaneously, and have a long endurance: a second view produceth nearly the same pleasure with the first. Love, hatred, and some other passions, increase gradually to a certain pitch, and thereafter decay gradually. Envy, malice, pride, scarce ever decay. Again, some passions, such as gratitude and revenge, are often exhausted by a single act of gratification. Other passions, such as pride, malice, envy, love, hatred, are not so exhausted; but having a long continuance, demand frequent gratification.