I will now speak of a strange doctrine, which is regarded by many as the crown of philosophy.  They affirm that all things come into being either by art or nature or chance, and that the greater things are done by nature and chance, and the lesser things by art, which receiving from nature the greater creations, moulds and fashions all those lesser works which are termed works of art.  Their meaning is that fire, water, earth, and air all exist by nature and chance, and not by art; and that out of these, according to certain chance affinities of opposites, the sun, the moon, the stars, and the earth have been framed, not by any action of mind, but by nature and chance only.  Thus, in their opinion, the heaven and earth were created, as well as the animals and plants.  Art came later, and is of mortal birth; by her power were invented certain images and very partial imitations of the truth, of which kind are the creations of musicians and painters:  but they say that there are other arts which combine with nature, and have a deeper truth, such as medicine, husbandry, gymnastic.  Also the greater part of politics they imagine to co-operate with nature, but in a less degree, having more of art, while legislation is declared by them to be wholly a work of art.  ‘How do you mean?’ In the first place, they say that the Gods exist neither by nature nor by art, but by the laws of states, which are different in different countries; and that virtue is one thing by nature and another by convention; and that justice is altogether conventional, made by law, and having authority for the moment only.  This is repeated to young men by sages and poets, and leads to impiety, and the pretended life according to nature and in disobedience to law; for nobody believes the Gods to be such as the law affirms.  ’How true! and oh! how injurious to states and to families!’ But then, what should the lawgiver do?  Should he stand up in the state and threaten mankind with the severest penalties if they persist in their unbelief, while he makes no attempt to win them by persuasion?  ’Nay, Stranger, the legislator ought never to weary of trying to persuade the world that there are Gods; and he should declare that law and art exist by nature.’  Yes, Cleinias; but these are difficult and tedious questions.  ’And shall our patience, which was not exhausted in the enquiry about music or drink, fail now that we are discoursing about the Gods?  There may be a difficulty in framing laws, but when written down they remain, and time and diligence will make them clear; if they are useful there would be neither reason nor religion in rejecting them on account of their length.’  Most true.  And the general spread of unbelief shows that the legislator should do something in vindication of the laws, when they are being undermined by bad men.  ’He should.’  You agree with me, Cleinias, that the heresy consists in supposing earth, air, fire, and water to be the first of all things.  These the heretics call nature, conceiving