The severer kinds of purification are practised when great offenders are punished by death or exile, but there is a milder process which is necessary when the poor show a disposition to attack the property of the rich, for then the legislator will send them off to another land, under the name of a colony.

In our case, however, we shall only need to purify the streams before they meet.

This is often a troublesome business, but in theory we may suppose the operation performed, and the desired purity attained.

Evil men we will hinder from coming, and receive the good as friends.
Like the old Heraclid colony, we are fortunate in escaping the abolition of debts and the distribution of land, which are difficult and dangerous questions.

But, perhaps, now that we are speaking of the subject, we ought to say how, if the danger existed, the legislator should try to avert it.