Before discussing the origins or the effects of feudalism it is well to form a definite conception of the system as we find it in the twelfth and thirteenth centuries, when it is the basis of local government, of justice, of legislation, of the army and of all executive power. In this period the lawyers have arrived at the doctrine that all lands is held from the King either mediately or directly. The King is himself a great landowner with demesnes scattered over the length and breadth of the realm; the revenues of these estates supply him with the larger part of his permanent income. The King is surrounded by a circle of tenants-in-chief, some of whom are bishops and abbots and ecclesiastical dignitaries of other kinds; the remainder are dukes, counts, barons, knights. All of these, laymen and churchmen alike, are bound to perform more or less specific services in return for their lands; the most important is military service, with a definite quota of knights, which they usually render at their own charge; but they are also liable to pay aids (auxilia) of money in certain contingencies, to appear regularly at the King's council and to sit as assessors in his law court. They hold their lands in fact upon a contract; but the precise obligations named in this contract do not exhaust their relation to the King. In a vague and elastic sense they owe him honour (obsequium) and loyalty (fidelitas). They must do all in their power to uphold his interests and exalt his dignity. He on his side is bound to consult them collectively, in all matters of importance, and to maintain them individually in the rights and possessions which he has granted to them. These personal and indefinite ties should not be renounced, on either side, without some very serious reason - gross treachery, gross neglect of duty, gross abuse of power or privilege.
These tenants-in-chief have on their estates a number of sub-tenants, who are bound to them by similar contracts and a similar personal relation. The homage of the sub-tenant to his immediate lord ought to be qualified by a reservation of the allegiance which all subjects owe to the King. Whether this reservation shall be made or, when made, shall have any practical consequences, will depend upon the King's resources and personality. Where effective, it means that he can claim from the sub-tenants the discharge of certain national duties, can call on them for military service, can judge them in his court, can tax them with the consent of his council, that is of their lords; on the other hand, it means that these sub-tenants may not allege the commands of their lord as an excuse for making war upon the King or committing any breach of the public peace. Where the general duty of allegiance has lapsed into oblivion, the tenant-in-chief is in all but name a dependent king, and the feudal state becomes a federation under a hereditary president, who occasionally arbitrates between the members of the federation and occasionally leads them out to war.