Definition
A Latin maxim meaning "to infinity" or "without limit." In legal usage, in infinitum signifies indefinite continuation, succession, or extension — particularly in the context of chains of title, lines of descent, feudal tenure obligations, or the theoretical perpetuation of interests in property. It describes something that, by its nature or by legal operation, would continue without a defined endpoint if left unchecked.
The phrase most commonly appears in two contexts:
1. Property and tenure law: Describing the theoretical extension of feudal services or subinfeudation down a chain of tenure without limit — a problem that prompted legislative intervention (notably the Statute of Quia Emptores, 1290) to prevent the proliferation of mesne lords in infinitum.
2. Logical and procedural argument: Invoked to flag a reductio ad absurdum — the point at which a legal rule or chain of reasoning, if extended without limit, produces an untenable or unworkable result. Courts and commentators use it to justify drawing a line where the law would otherwise spiral into indefinite complexity.
Common Language
Modern common usage (Wiktionary): Listed as an alternative form of ad infinitum — meaning endlessly, without limit, going on forever.
Historical common usage: The phrase was not separately treated in Webster's 1913 as distinct from ad infinitum; both were understood as Latin expressions meaning "to infinity," used in general discourse to denote endless repetition or continuation.
Editorial note: The gap between common and legal usage is one of context, not meaning. Colloquially, in infinitum simply means "forever" or "endlessly." In legal sources, it carries a more pointed function — it signals a structural problem in a legal rule or property arrangement, identifying the moment where indefinite extension becomes legally intolerable. Encountering the phrase in a legal text is therefore a flag for doctrinal argument, not mere description.
Common Confusion
In infinitum and ad infinitum are functionally interchangeable in most historical legal texts and are treated as such by the historical dictionaries. Researchers should not read significance into an author's choice of one over the other. Both signal the same concept. Some modern legal writers prefer ad infinitum as the more familiar Latin form; in infinitum appears more frequently in older common law treatises and Year Books contexts.
Why It Matters in Research
The phrase is primarily encountered in three research contexts, each requiring different navigation:
First, feudal tenure and property history. In infinitum appears heavily in discussions of subinfeudation — the practice by which a tenant granted land to a subtenant, who could in turn grant further down, creating chains of tenure extending theoretically without end. The Statute of Quia Emptores (18 Edw. I, 1290) is the landmark response to this problem. Any research into medieval land law, fee simple alienation, or the abolition of feudal incidents will encounter this phrase as a structural marker. Blackstone's Commentaries on the Laws of England uses the concept to explain why subinfeudation became untenable.
Second, logical argument in judicial opinions and treatises. When a court writes that extending a principle in infinitum would produce absurd results, the phrase functions as a rhetorical and doctrinal stop. It signals that the court is drawing a limiting principle. Researchers working with historical equity or common law reasoning — particularly in nuisance, easements, or privity — will encounter this usage and should read it as the court's justification for restricting a rule's scope.
Third, succession and descent. The phrase appears in discussions of indefinite succession of heirs or the theoretical perpetuation of entailed estates. Its appearance in that context often signals engagement with the rule against perpetuities or its predecessors.
A research trap: because the phrase is Latin and appears without definition in older sources, it can be skimmed past. But its presence in a primary source almost always marks a point of legal stress — where the author is arguing that something cannot or should not continue without limit. Treat it as a signal to read closely.
Historical Dictionary Support
The three shelf sources are in close agreement. Black's (both editions) define the phrase as "infinitely; indefinitely" and note that it "imports indefinite succession or continuance." Bouvier adds "imports to infinity" without elaboration. All three treat the phrase as a term of art describing unlimited extension, particularly in the property context.
What the historical dictionaries do not capture is the argumentative function of the phrase — its use as a doctrinal stop or reductio flag. This omission is understandable given the dictionary format, but it means researchers relying solely on these definitions will understand the phrase's literal meaning without grasping its rhetorical and structural role in legal texts. Blackstone and the institutional writers are more useful on that dimension than the dictionaries alone.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Feudal Tenure; Rule Against Perpetuities; Subinfeudation; Quia Emptores.