Generally speaking, therefore, it is necessary, both that the being in progress toward a state conformable to nature should be pleasant; and that, in the highest degree, when those feelings, whose original is conformable to it, shall have recovered that their nature; and habits, because that which is habitual becomes by that time natural, as it were; for, in a certain way, custom is like nature, because the idea of frequency is proximate to that of always; now nature belongs to the idea of always, custom to that of often. What is not compulsory, also, is pleasant; for compulsion is contrary to nature. Wherefore acts of necessity are painful; and it has been truly remarked, "Every act of necessity is in its nature painful." It must be also that a state of sedulous attention, anxiety, the having the mind on the stretch, are painful, for they all are acts of necessity, and constrained, unless they have become habitual; but it is custom which, under such circumstances, renders them pleasant. The contraries of these must also be pleasant; wherefore, relaxation of mind, leisure, listlessness, amusements, and intervals of rest, rank in the class of things pleasant; for none of these has anything to do with necessity. Everything of which there is an innate appetite, is pleasant; for appetite is a desire of what is pleasant. Now, of appetites, some are irrational, others attended by reason. I call all those irrational which men desire, not from any conception which they form: of this kind are all which are said to exist naturally, as those of the body; thirst or hunger, for instance, in the case of sustenance; and the appetite of sustenance in every kind. And the appetites connected with objects of taste, and of lust, and, in fact, objects of touch generally; the appetite of fragrant odors, too, as connected with smelling, and hearing, and sight. Appetites attended by reason are all those whatsoever which men exercise from a persuasion: for many things there are which they desire to behold, and possess, on hearsay and persuasion. Now, as the being pleased stands in the perception of a certain affection, and as imagination is a kind of faint perception, there will attend on him who exercises either memory or hope a kind of imagination of that which is the object of his memory or hope; but if so, it is plain that they who exercise memory or hope, certainly feel pleasure, since they have also a perception. So that everything pleasant consists either in the perception of present objects, or in the remembrance of those which have already been, or in the hope of such as are yet to be; for men exercise perception on present, memory on past, and hope on future objects. Now the objects of memory are pleasant, not only such as at the moment while present were pleasant, but some even which were not pleasant, should their consequence subsequently be honorable and good; and hence this saying, "But it is indeed pleasant for a man, when