Definition
A Latin phrase meaning "at that very instant" or "immediately." Used in legal texts and judicial opinions to indicate that a legal consequence, change of status, or operative effect occurs at the precise moment of a triggering act — not after a delay, not upon subsequent formality, but simultaneously with and inseparable from the act itself. The phrase functions as a temporal marker of exactness, emphasizing that no interval of time, however brief, separates the cause from its legal effect.
Why It Matters in Research
Eo instante appears almost exclusively in older English common law materials and in American cases and treatises that draw directly on those sources. Researchers encountering the phrase in 18th- or 19th-century texts should recognize it as a term of art signaling instantaneous legal effect — typically in contexts involving vesting of property rights, merger of estates, changes in legal status, or the moment at which a legal disability attaches or dissolves.
The phrase is frequently paired with discussions in Blackstone's Commentaries and Coke on Littleton, where questions of precisely when a right vests or a status changes were technically significant — particularly in property law, where the sequence of seisin, the moment of conveyance taking effect, or the instant at which a condition was fulfilled could determine outcomes. Researchers working in those sources should watch for eo instante as a signal that the author is making a precise temporal argument, not a general statement about speed.
The term largely disappeared from American legal writing through the 20th century, replaced by plain-English formulations such as "immediately upon," "at the moment of," or "automatically." Its presence in a source is therefore also a rough dating indicator. A modern court using eo instante is almost certainly quoting or paraphrasing an older authority.
Do not mistake the phrase for mere rhetorical emphasis. When a historical source says a right vests eo instante, it is making a substantive legal claim about simultaneity — that the right and its occasion are legally inseparable. That distinction can matter when tracing the doctrinal history of automatic vesting rules, instantaneous merger, or the moment a contract becomes operative.
Historical Dictionary Support
All four shelf sources agree precisely on meaning: "at that instant," "at the very or same instant," "immediately." The uniformity here is notable — there is no dispute or evolution in the definition itself across any of these authorities.
Rapalje & Lawrence is the most spare ("at that very instant"), while Burrill and both Black's editions provide the same cluster of citations: Blackstone's Commentaries (1 Bl. Comm. 196, 249; 2 Bl. Comm. 168), Coke on Littleton (298a), and 1 Coke 138. This citation cluster points researchers directly to the primary materials where the phrase does its work. The references to Blackstone's first volume (concerning rights of persons and their legal incidents) and second volume (concerning property rights and real property law) suggest the term was employed across both status-based and property-based legal questions.
What the historical dictionaries do not provide is context for how the phrase functions in argument — they define it as a translation but do not explain why instantaneity was legally significant in the passages cited. Researchers should not treat the dictionary entry as a substitute for consulting the cited passages in Blackstone and Coke directly.