Definition
Expromission is a form of novation drawn from the civil law in which a new debtor is substituted for an existing debtor, and the original debtor is discharged from the obligation by the creditor's acceptance of the substitution. The key features are threefold: a new party steps in, the old party steps out, and the creditor's consent to that exchange is what makes it operative. Unlike a simple assignment of debt or the addition of a surety, expromission extinguishes the original debtor's liability entirely. The creditor looks solely to the new debtor going forward.
The concept belongs to the broader category of novation — the substitution of a new obligation for an old one — but expromission specifically denotes the subclass involving substitution of a person (novation by change of debtor), as distinguished from novation by change of creditor or novation by change of the obligation's subject matter.
---
Common Confusion
Expromission is easily conflated with delegation (delegatio) and with suretyship. Delegation also involves a new debtor but does not necessarily release the original — the original debtor may remain liable unless the creditor expressly agrees to release. Expromission requires that release; it is the creditor's agreement to discharge the old debtor that distinguishes it. Suretyship adds a new obligor alongside the existing debtor, with no discharge at all. In research, conflation of these three concepts is common in older common-law sources, which sometimes used "novation" loosely to cover all three.
---
Why It Matters in Research
Expromission is a term of art confined almost entirely to civil law sources. Researchers working in common-law jurisdictions will rarely encounter it in domestic case law or statutes, but will meet it frequently in: (1) treatises and commentaries drawing on Roman law foundations, including works on contract and obligation; (2) Scottish, Louisiana, Quebec, and South African legal materials, where the civil law tradition remains operative; and (3) comparative law scholarship on novation and debt discharge.
The term's practical significance in historical common-law research is limited, but its conceptual significance is high. Courts in common-law jurisdictions working through novation problems — especially whether an original debtor was discharged or merely joined by a new obligor — were often reasoning through the same distinctions Roman law codified under this term, without using the word. A researcher tracing the doctrinal history of novation-by-debtor-substitution should understand expromission as the civil law anchor of that doctrine.
Be alert to the fragmented nature of the Rapalje & Lawrence entry (see Historical Dictionary Support below), which suggests the original source text ran across multiple headwords or was imperfectly excerpted. Cross-referencing the Sanders Justinian citation is essential before relying on any passage attributed to that entry.
---
Historical Dictionary Support
Rapalje & Lawrence define expromission as "a species of novation in the civil law; as a creditor's acceptance of a new debtor, who takes the place of the old debtor, who is discharged," citing Sanders' Justinian (5th ed., p. 389). This definition is clean and accurate as far as it goes. The Wiktionary definition is substantively identical, framing it as "the intervention of a new debtor, substituted for the former one, who is consequently discharged by the creditor."
A caution for researchers: the Rapalje & Lawrence entry as reproduced here contains what appears to be text corruption or a splicing artifact. Following the Sanders citation, the entry shifts without transition to material concerning "immediate extents," scire facias procedure, and a reference to Stat. 57 Geo. III c. 117. This material has no relationship to expromission and almost certainly belongs to a different headword (likely EXTENT or a related process term). Researchers should treat the post-citation text in that entry as unreliable for expromission purposes and consult the Sanders Justinian citation directly.
Historical legal dictionaries generally agree on the core meaning. The civilian tradition is consistent: expromission requires the creditor's active consent to the substitution, without which the transaction is mere delegation with the original debtor remaining on the hook. Sources diverge only in how they characterize the creditor's consent — some treat it as implicit in acceptance of the new debtor's promise, others require express discharge. This distinction carries forward into modern comparative law debates about novation requirements.
---
Jurisdictional Note
The term is operative law in civil law jurisdictions including Louisiana, Quebec, and Scotland, where codes and common law borrowings from the Roman tradition give it practical application. In common-law jurisdictions (England, most U.S. states), the underlying concept is absorbed into general novation doctrine without the specific label; courts ask whether the creditor agreed to release the original debtor, but do not use "expromission" as a term of art.
---