William Blackstone,
Commentaries on the Laws of England
(1768)
“ Heirs apparent are such, whose right of inheritance is indefeasible, provided they outlive the ancestor; as the eldest son or his issue, who must by the course of the common law be heirs to the father whenever he happens to die. Heirs presumptive are such, who, if the ancestor should die immediately, would in the present circumstances of things be his heirs; but whose right of inheritance may be defeated by the contingency of some nearer heir being born: as a brother, or nephew, whose presumptive succession may be destroyed by the birth of a child ”
