Definition
A Latin maxim meaning "together and at one time." Used in procedural and pleading contexts to describe acts or obligations that must be performed simultaneously and as a single, unified event rather than sequentially or in installments. The phrase captures the idea that multiple parties acted in concert at a single moment, or that a legal duty or right arises and must be discharged all at once.
Common Confusion
Simul et semel is frequently confused with simul cum ("together with"), which appears in a different and more common pleading context — namely, indictments or declarations naming certain defendants while alleging they acted alongside unnamed others. The two phrases share the word simul but function differently. Simul cum is additive, joining known and unknown parties in an allegation. Simul et semel is temporal and structural, asserting that an act or obligation occurred or must be performed as a single simultaneous event. In a historical text, context usually resolves the distinction, but researchers scanning Latin phrases should not treat the two as interchangeable.
Why It Matters in Research
Researchers encounter simul et semel most often in two contexts. First, in historical pleading — particularly in declarations and indictments — the phrase signals joint participation at a single moment, closely related to the simul cum construction (alleging that named defendants acted "together with" unnamed others). Confusing simul et semel with simul cum is easy in older pleading texts; they are distinct phrases serving distinct functions. Second, the phrase appears in obligations and contract law to describe a duty that is entire and indivisible, arising at one time and payable or performable at one time — as opposed to obligations that can be satisfied piecemeal. If you are tracing a legal argument about whether a party was required to perform all at once or could perform in parts, this phrase in a historical source is a signal that the court or pleader was treating the obligation as entire and simultaneous.
The phrase appears in texts referencing Fleta (the 13th-century English legal treatise) and in Saunders' Reports, meaning you will find it anchored in English common law procedural history. Modern sources rarely use the phrase directly; researchers should not expect it in contemporary American cases. When it appears in a digitized historical corpus, it is almost always a pleading or procedural term and should be read in that light.
Historical Dictionary Support
The historical dictionaries are in close agreement. Black's (1st and 2nd editions) and Burrill all give the same core translation: "together and at one time." Burrill adds the most value by anchoring the phrase to specific sources — Fleta, lib. 2, c. 47, § 5, and 1 Saunders 323a, note 6 — confirming that the phrase had active use in English common law pleading well before it migrated into American legal vocabulary through treatise tradition.
Black's 1st edition is worth reading carefully because it places the phrase in direct proximity to the simul cum construction used in indictments, suggesting that editors understood these as related but distinct concepts. No historical dictionary provides a sustained doctrinal discussion, and none traces the phrase's use into American jurisprudence specifically. Researchers should treat the historical dictionary entries as confirmatory of translation and origin, not as guides to doctrinal application.
Jurisdictional Note
The phrase is rooted in English common law and appears primarily in pre-20th-century Anglo-American sources. It carries no distinct modern American statutory meaning and is not defined in current uniform codes or restatements. Jurisdictional variation is therefore not a meaningful research variable; the phrase is effectively a historical artifact of common law pleading and obligation doctrine.