Definition
*Bastardus non potest* is a Latin maxim of the common law meaning, in full, *bastardus non potest habere haeredem de corpore suo legitime procreatum* — "a bastard cannot have an heir of his body lawfully begotten." In its shortened form, the phrase encapsulates the rule that a person born outside of lawful marriage was, under the traditional common law of inheritance, incapable of transmitting heritable blood to legitimate descendants for purposes of intestate succession through the bloodline.
The maxim operated as part of the broader common law doctrine of bastardy, under which a person classified as a bastard (filius nullius — "son of nobody") stood outside the ordinary chain of descent. A bastard could acquire property by purchase or devise, but could not inherit through the general law of descent, and — under the strictest formulation of the rule — could not transmit inheritable blood upward to ancestors or, in some applications, downward to descendants in the context of tracing a legitimate line of descent.
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Common Confusion
The maxim is sometimes loosely paraphrased as meaning simply that a bastard cannot inherit at all. This overstates the rule. The more precise operation was that a bastard stood at the beginning and end of his own line of descent: he could inherit from no one by blood and, under the fuller maxim, could not serve as a conduit through whom legitimate descendants traced a heritable bloodline. The two propositions — inability to inherit *from* blood relations and inability to transmit heritable blood *through* — are related but distinct.
The maxim should also be distinguished from the civil law treatment of illegitimacy, which was considerably more flexible and admitted paths to legitimation unavailable at common law.
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Why It Matters in Research
This maxim appears in English common law treatises and abridgments from the medieval period through the eighteenth and nineteenth centuries, most prominently in discussions of descent, inheritance, and the law of bastardy. Researchers using historical sources should be alert to several points.
First, the maxim is a compressed fragment. Historical sources — including Blackstone, Bracton, and Coke — treat the fuller doctrine at length, but the shortened phrase *bastardus non potest* often appears without the completing clause. Identifying which portion of the bastardy doctrine a source is invoking requires reading in context.
Second, the practical reach of the maxim changed dramatically with legislative reform. In England, the Legitimacy Act 1926 and subsequent legislation significantly altered the status of children born outside marriage. In the United States, a series of Supreme Court decisions beginning in the late twentieth century applied equal protection principles to illegitimacy classifications, effectively dismantling the common law rule in the inheritance context across most American jurisdictions. Modern researchers should not assume the maxim describes current law anywhere in the common law world without checking current statutory and constitutional developments.
Third, the maxim intersects with the common law concept of *filius nullius*. Corpus searches on bastardy, descent, and intestate succession will benefit from cross-referencing both Latin terms, as sources use them interchangeably or in tandem.
Fourth, the source fragment available from Black's 2nd Edition is incomplete and appears to have been extracted from a discussion of Roman or Byzantine law rather than from a dedicated entry on this maxim. Researchers relying on Black's should treat the surviving text as contextual background only and consult the fuller common law treatise literature for substantive doctrine.
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Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) provides only a partial text in the available source material, which appears to concern the Eastern Roman (Byzantine) legal tradition and the fall of Constantinople in 1453, rather than offering a direct treatment of the maxim itself. This fragment likely appeared in a broader discussion of the civil law heritage that influenced common law bastardy rules, but it cannot be used to reconstruct Black's full entry.
The maxim itself has deep roots in English common law literature. Bracton's *De Legibus et Consuetudinibus Angliae* addressed the incapacity of bastards in the law of descent. Coke on Littleton and Blackstone's *Commentaries* each treat bastardy as a defined status with specific consequences for inheritance. The civilian tradition — referenced obliquely in the Black's fragment — handled illegitimacy differently, allowing legitimation by subsequent marriage (*legitimatio per subsequens matrimonium*), a doctrine that English common law long refused to recognize and that created persistent conflict between church courts (which applied canon law) and royal courts (which applied common law) over questions of bastardy determinations.
Historical dictionaries that address this maxim tend to present the classical common law rule without acknowledging the later legislative and constitutional erosion of its force — a significant gap for any researcher working on materials after the mid-twentieth century.
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Jurisdictional Note
The doctrine encoded in this maxim has been substantially abrogated by statute and constitutional decision across common law jurisdictions. American states have largely equalized inheritance rights of children regardless of marital status of parents, though specific rules on intestate succession still vary. English law has undergone successive statutory reforms. Researchers should treat this maxim as descriptive of historical doctrine, not current law.
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