The diffusion of Primogeniture is usually accounted for by assigning what are called Feudal reasons for it. It is asserted that the feudal superior had a better security for the military service he required when the fief descended to a single person, instead of being distributed among a number on the decease of the last holder. Without denying that this consideration may partially explain the favour gradually acquired by Primogeniture, I must point out that Primogeniture became a custom of Europe much more through its popularity with the tenants than through any advantage it conferred on the lords. For its origin, moreover, the reason given does not account at all. Nothing in law springs entirely from a sense of convenience. There are always certain ideas existing antecedently on which the sense of convenience works, and of which it can do no more than form some new combination; and to find these ideas in the present case is exactly the problem.
A valuable hint is furnished to us from a quarter fruitful of such indications. Although in India the possessions of a parent are divisible at his death, and may be divisible during his life, among all his male children in equal shares, and though this principle of the equal distribution of _property_ extends to every part of the Hindoo institutions, yet wherever _public office_ or _political power_ devolves at the decease of the last Incumbent, the succession is nearly universally according to the rules of Primogeniture. Sovereignties descend therefore to the eldest son, and where the affairs of the Village Community, the corporate unit of Hindoo society, are confided to a single manager, it is generally the eldest son who takes up the administration at his parent's death. All offices, indeed, in India, tend to become hereditary, and, when their nature permits it, to vest in the eldest member of the oldest stock. Comparing these Indian successions with some of the ruder social organisations which have survived in Europe almost to our own day, the conclusion suggests itself that, when Patriarchal power is not only _domestic_ but _political_, it is not distributed among all the issue at the parent's death, but is the birthright of the eldest son. The chieftainship of a Highland clan, for example, followed the order of Primogeniture. There seems, in truth, to be a form of family-dependency still more archaic than any of those which we know from the primitive records of organised civil societies. The Agnatic Union of the kindred in ancient Roman law, and a multitude of similar indications, point to a period at which all the ramifying branches of the family tree held together in one organic whole; and it is no presumptuous conjecture, that, when the corporation thus formed by the kindred was in itself an independent society, it was governed by the eldest male of the oldest line. It is true that we have no actual knowledge of any such society. Even in the most elementary communities, family-organisations, as we know them, are at most _imperia in imperio_. But the position of some of them, of the Celtic clans in particular, was sufficiently near independence within historical times to force on us the conviction that they were once separate _imperia_, and that Primogeniture regulated the succession to the chieftainship. It is, however, necessary to be on our guard against modern associations with the term of law. We are speaking of a family-connection still closer and more stringent than any with which we are made acquainted by Hindoo society or ancient Roman law. If the Roman Paterfamilias was visibly steward of the family possessions, if the Hindoo father is only joint-sharer with his sons, still more emphatically must the true patriarchal chieftain be merely the administrator of a common fund.