Definition of Special Assumpsit:

“(17c.) An action based on the defendant’s breach of an express contract. — Also termed express assumpsit.”

     “Special assumpsit lies for the recovery of damages for the breach of simple contract, either express or implied in fact. The term ‘special contract’ is often used to denote an express or explicit contract at contrasted with a promise implied in law.”

• Benjamin J. Shipman, Handbook of Common-Law Pleading § 58, at 148 (Henry Winthrop Ballantine ed., 3d ed. 1923)

     “From the allegations concerning the ‘assumpsit’, a new action which split off from the action on the case came to be known as the action of assumpsit. Since, however, the plaintiff had to allege & prove a specific or special promise, in order to get a judgment, the action came to be known as the action of ‘special assumpsit’. When the special promise came to be regarded as the bases of the action, the action came to be regarded as a contract action, rather than one based on unclassified ‘wrongs’.”

• Charles Herman Kinnane, A First book on Anglo-American Law 633-34 (2nd ed. 1952)

Definition of ASSUMPSIT:

“[Law Latin ‘he undertook’] (16c.) 1. An express or implied promise, not under seal, by which one person undertakes to do some act or pay something to another <an assumpsit to pay a debt>.  2. A common-law action for breach of such a promise or for breach of contract <the creditor’s assumpsit against the debtor>.”

     “It was early known as ‘trespass on the case upon promises’, but in time came to be designated assumpsit he assumed or promised), & lies for damages for breach of all contracts, parol or simple, whether written or verbal, express or implied.”

• Edwin E. Bryant, the Law of Pleading Under the Codes of Civil Procedure 9-10 (2d ed. 1899)

“ASSUMPSIT” continued:

     “In its origin an action of tort, ”[assumpsit] was soon transformed into an action of contract, becoming afterwards a remedy where there was neither tort nor contract. Based at first only upon an express promise, it was afterwards supported upon an implied promise, & even upon a fictitious promise. Introduced as a special manifestation of the action on the case, it soon acquired the dignity of a distinct form of action, which superseded Debt, became concurrent with Account, with Case upon a bailment (page 65), a warranty, & the essentially equitable quasi-contracts growing out of the principle of unjust enrichment (page 44). Surely, it would be hard to find a better illustration of the flexibility & power of self-development of the Common Law.”

– James Barr Ames, “The History of Assumpsit” in 3 Select Essays in Anglo-American Legal History 298 (1909)