Definition
A double possibility is a contingency built upon another contingency — that is, a possibility upon a possibility. In property law, the concept arises when a future interest or remainder is made to depend on two successive uncertain events, neither of which has occurred. Because the vesting of such an interest requires both contingencies to be resolved in favor of the grantee, courts of equity and common law treated double possibilities with deep suspicion, and in many contexts refused to enforce them as void for remoteness or as contrary to policy favoring the alienability of property.
The classic formulation, traced to Blackstone (2 Bl. Comm. 170), treats the double possibility as the limiting case of contingent remainders: if a single contingency already renders a remainder uncertain, stacking a second contingency on top of the first pushes the interest beyond what the common law would recognize as capable of vesting within an acceptable time.
Common Confusion
Double possibility is not the same as the Rule Against Perpetuities, though the underlying policy concern — preventing property from being tied up on remote and speculative conditions — is shared. The Rule Against Perpetuities is a formal, survivable test (an interest is void if it might not vest within a life in being plus twenty-one years); a double possibility was treated at common law as categorically suspect regardless of the time frame. Researchers should not import modern Rule Against Perpetuities analysis wholesale into older materials that invoke double possibility.
Why It Matters in Research
This term is almost entirely a creature of pre-modern English property law and appears in American sources chiefly in discussions of contingent remainders, the Rule Against Perpetuities, and the history of future interests. Researchers encountering the phrase in nineteenth-century American treatises or court opinions should understand it as a doctrinal ancestor, not a term of active modern practice.
The trap in historical sources is conflation: writers sometimes use "double possibility" loosely to mean any highly speculative contingent remainder, while others use it technically to mean a remainder that requires two distinct contingent events before it can vest. The distinction matters because only the technical sense carries the full weight of common law hostility — courts treating such interests as void ab initio, not merely as remote.
Researchers working through older conveyancing disputes or wills cases in the Law Mind corpus should trace the term to the contingent remainder doctrine rather than to the Rule Against Perpetuities directly. The Rule Against Perpetuities emerged partly as a codification of the concern underlying double possibilities, but the two are not interchangeable: the Rule operates by a time-limit test, while the double possibility objection was a categorical hostility to stacking contingencies regardless of when they might resolve.
Connection to Bouvier's cross-reference to CONTINGENT REMAINDER is essential. Any corpus search on double possibility that does not also pull contingent remainder materials will miss the substantive doctrinal context.
Historical Dictionary Support
Both Black's and Bouvier's provide identical, minimal definitions — "a possibility upon a possibility" — and both cite exclusively to 2 Blackstone's Commentaries 170. Neither dictionary elaborates on the practical consequences of a double possibility, nor do they distinguish between the common law rule against such interests and later statutory or equitable modifications. Bouvier adds only the cross-reference to CONTINGENT REMAINDER, which is the more useful navigational pointer.
The brevity of these entries is itself informative: by the time both dictionaries were in wide use, the double possibility had largely ceased to be a live doctrinal issue. It survived in the literature as a historical marker of the common law's structural hostility to highly contingent future interests rather than as a rule courts applied with regularity. What historical sources miss entirely is any discussion of how American jurisdictions received or modified the English rule, or how the concept dissolved into the broader framework of the Rule Against Perpetuities.
Encyclopedia Cross-Reference
The Law Mind Property Law Encyclopedia: Future Interests — Reversion, Possibility of Reverter, Right of Entry (property_5). This entry provides the structural framework of future interests within which the double possibility doctrine operates.