In every art and science which is not conversant in parts but in some one genus in which it is complete, it is the business of that art alone to determine what is fitted to its particular genus; as what particular exercise is fitted to a certain particular body, and suits it best: for that body which is formed by nature the most perfect and superior to others necessarily requires the best exercise-and also of what one kind that must be which will suit the generality; and this is the business of the gymnastic arts: and although any one should not desire to acquire an exact knowledge and skill in these exercises, yet it is not, on that account, the less necessary that he who professes to be a master and instruct the youth in them should be perfect therein: and we see that this is what equally befalls the healing, shipbuilding, cloth-making, and indeed all other arts; so that it evidently belongs to the same art to find out what kind of government is best, and would of all others be most correspondent to our wish, while it received no molestation from without: and what particular species of it is adapted to particular persons; for there are many who probably are incapable of enjoying the best form: so that the legislator, and he who is truly a politician, ought to be acquainted not only with that which is most perfect imaginable, but also that which is the best suited to any given circumstances. There is, moreover, a third sort, an imaginary one, and he ought, if such a one should be presented to his consideration, to be able to discern what sort of one it would be at the beginning; and, when once established, what would be the proper means to preserve it a long time. I mean, for instance, if a state should happen not to have the best form of government, or be deficient in what was necessary, or not receive every advantage possible, but something less. And, besides all this, it is necessary to know what sort of government is best fitting for all cities: for most of those writers who have treated this subject, however speciously they may handle other parts of it, have failed in describing the practical parts: for it is not enough to be able to perceive what is best without it is what can be put in practice. It should also be simple, and easy for all to attain to. But some seek only the most subtile forms of government. Others again, choosing [1289a] rather to treat of what is common, censure those under which they live, and extol the excellence of a particular state, as the Lacedaemonian, or some other: but every legislator ought to establish such a form of government as from the present state and disposition of the people who are to receive it they will most readily submit to and persuade the community to partake of: for it is not a business of less trouble to correct the mistakes of an established government than to form a new one; as it is as difficult to recover what we have forgot as to learn anything afresh. He, therefore, who aspires to the character of a legislator, ought, besides all we have already said, to be able to correct the mistakes of a government already established, as we have before mentioned. But this is impossible to be done by him who does not know how many different forms of government there are: some persons think that there is only one species both of democracy and oligarchy; but this is not true: so that every one should be acquainted with the difference of these governments, how great they are, and whence they arise; and should have equal knowledge to perceive what laws are best, and what are most suitable to each particular government: for all laws are, and ought to be, framed agreeable to the state that is to be governed by them, and not the state to the laws: for government is a certain ordering in a state which particularly respects the magistrates in what manner they shall be regulated, and where the supreme power shall be placed; and what shall be the final object which each community shall have in view; but the laws are something different from what regulates and expresses the form of the constitution-it is their office to direct the conduct of the magistrate in the execution of his office and the punishment of offenders. From whence it is evident, that the founders of laws should attend both to the number and the different sorts of government; for it is impossible that the same laws should be calculated for all sorts of oligarchies and all sorts of democracies, for of both these governments there are many species, not one only.