  But the function argument concludes that justice is both necessary  and sufficient for happiness (354a), and this is a considerably  stronger thesis than the claim that the just are always happier than  the unjust. After the challenge Glaucon and Adeimantus present,  Socrates might not be so bold. Even if he successfully maintains that acting justly is identical to being happy, he might think that there are circumstances in which no just person could act justly and thus be happy. This will nonetheless satisfy Glaucon and  Adeimantus if the just are better off (that is, closer to happy) than the unjust in these circumstances. (See also Kirwan 1965 and Irwin 1999.)