For those desires which proceed from nature are easily satisfied without any injustice; but those which are vain ought not to be complied with. For they desire nothing which is really desirable; and there is more disadvantage in the mere fact of injustice than there is advantage in what is acquired by the injustice. Therefore a person would not be right who should pronounce even justice intrinsically desirable for its own sake; but because it brings the greatest amount of what is agreeable. For to be loved and to be dear to others is agreeable because it makes life safer, and pleasure more abundant. Therefore we think dishonesty should be avoided, not only on account of those disadvantages which befal the wicked, but even much more because it never permits the man in whose mind it abides to breathe freely, and never lets him rest.
But if the praise of those identical virtues in which the discourse of all other philosophers so especially exults, cannot find any end unless it be directed towards pleasure, and if pleasure be the only thing which calls and allures us to itself by its own nature; then it cannot be doubtful that that is the highest and greatest of all goods, and that to live happily is nothing else except to live with pleasure.
XVII. And I will now explain in a few words the things which are inseparably connected with this sure and solid opinion.
There is no mistake with respect to the ends themselves of good and evil, that is to say, with respect to pleasure and pain; but men err in these points when they do not know what they are caused by. But we admit that the pleasures and pains of the mind are caused by the pleasures and pains of the body. Therefore I grant what you were saying just now, that if any philosophers of our school think differently (and I see that many men do so, but they are ignorant people) they must be convicted of error. But although pleasure of mind brings us joy, and pain causes us grief, it is still true that each of these feelings originates in the body, and is referred to the body; and it does not follow on that account that both the pleasures and pains of the mind are not much more important than those of the body. For with the body we are unable to feel anything which is not actually existent and present; but with our mind we feel things past and things to come. For although when we are suffering bodily pain, we are equally in pain in our minds, still a very great addition may be made to that if we believe that any endless and boundless evil is impending over us. And we may transfer this assertion to pleasure, so that that will be greater if we have no such fear.