Since there are many forms of government there must be many varieties of citizen and especially of citizens who are subjects; so that under some governments the mechanic and the laborer will be citizens, but not in others, as, for example, in aristocracy or the so-called government of the best (if there be such an one), in which honors are given according to virtue and merit; for no man can practice virtue who is living the life of a mechanic or laborer. In oligarchies the qualification for office is high, and therefore no laborer can ever be a citizen; but a mechanic may, for an actual majority of them are rich. At Thebes there was a law that no man could hold office who had not retired from business for ten years. But in many states the law goes to the length of admitting aliens; for in some democracies a man is a citizen though his mother only be a citizen; and a similar principle is applied to illegitimate children; the law is relaxed when there is a dearth of population. But when the number of citizens increases, first the children of a male or a female slave are excluded; then those whose mothers only are citizens; and at last the right of citizenship is confined to those whose fathers and mothers are both citizens.