Definition
Diligence is the degree of care, attention, and effort that the law requires of a person given a particular situation or relationship. It is the positive standard against which conduct is measured — the inverse of negligence. Rather than asking what carelessness occurred, diligence asks what care was exercised.
The law historically organized diligence into three recognized degrees:
1. Slight diligence: The minimal care that even an inattentive person would exercise; the standard imposed on those who receive the exclusive benefit of a transaction (such as a gratuitous borrower in bailment law).
2. Ordinary diligence: The care that a reasonable person of average prudence exercises over their own affairs. This is the most common legal standard. It is variable in its application to specific facts but uniform in its underlying benchmark — the conduct of an ordinary, prudent person.
3. Extraordinary or great diligence: The high degree of care exercised by an unusually cautious person; required of those who hold property primarily for another's benefit or who carry special responsibility, such as common carriers of persons.
Beyond bailment law, the concept of diligence operates broadly across civil and criminal procedure, contract performance, and regulatory compliance — most prominently under the phrase "due diligence," which denotes the level of reasonable investigation or care appropriate to a given legal context.
Common Language
Modern common usage (Wiktionary): Steady application; industry; careful work involving long-term effort. The qualities of a hard worker, including conscientiousness, determination, and perseverance. Carefulness appropriate to a particular task or responsibility.
Historical common usage (Webster's 1913): The quality of being diligent; carefulness; careful attention — the opposite of negligence. Interested and persevering application; devoted and painstaking effort to accomplish what is undertaken.
The common-language definitions converge on personal virtue — industriousness, thoroughness, work ethic. The legal definitions are not about character but about measured standards of conduct imposed by law on specific actors in specific relationships. Legal diligence is objective and situational; common-language diligence is personal and aspirational. A researcher should also note that Webster's 1913 includes a Scottish legal meaning — diligence as a process for seizing persons or property for debt — which is discussed below.
Recognized Forms
/SUBTYPES
DUE DILIGENCE
In modern usage, due diligence refers to the reasonable investigation required before entering a transaction, making a representation, or relying on a legal right. It appears in securities law (the investigation required to establish a defense to liability for material misstatements), in corporate transactions (pre-acquisition investigation of a target company's assets, liabilities, and legal exposure), in intellectual property (review of ownership, encumbrances, and validity of IP assets before acquisition or financing), and in environmental law (investigation of contamination before acquiring real property). The standard of what is "due" varies by context and relationship.
DILIGENT PROSECUTION
In environmental citizen suits and related regulatory contexts, diligent prosecution refers to whether a governmental agency is actively and sufficiently enforcing a statutory violation, which can bar a private citizen suit. The standard is substantive, not merely formal — government action that is nominal or incomplete may not constitute diligent prosecution sufficient to preclude citizen enforcement.
DILIGENCE (SCOTS LAW / HISTORICAL PROCEDURAL)
In Scots law, and reflected in Webster's 1913, diligence historically referred to judicial process for enforcing obligations — the mechanism by which creditors could attach the person, land, or property of a debtor. This meaning is entirely distinct from the care-and-attention sense and has no counterpart in standard American common law usage. Researchers encountering this term in Scottish, early British, or mixed-jurisdiction sources should read carefully for context.
Why It Matters in Research
The three-degree framework for diligence — slight, ordinary, and extraordinary — is the classical structure for bailment analysis and appears consistently across the historical sources in this corpus. Researchers working with nineteenth-century case law or treatise material will encounter this framework as operative law. In modern American common law, the three-degree framework has largely collapsed: courts apply an ordinary-care or reasonable-person standard across most contexts, and the formal distinctions among degrees of diligence have diminished practical significance outside specialized bailment and carrier cases. Reading historical sources with this shift in mind prevents misapplication.
The phrase "due diligence" requires particular caution. In historical sources, it is a general standard of appropriate care. In modern transactional and securities practice, it has become a term of art with specialized procedural and substantive content specific to its context. A researcher moving between historical doctrine and modern deal practice should not treat these as equivalent without examining the governing framework.
The Scots procedural meaning of diligence is a live trap in mixed-jurisdiction research. It appears in Webster's 1913 without prominent flagging and can confuse researchers who encounter it in early American sources influenced by Scots or civil law traditions.
The three encyclopedia cross-references reflect the term's modern reach: due diligence in corporate acquisitions, IP-specific diligence in transactions, and the diligent-prosecution doctrine in environmental citizen suits. These are operationally distinct contexts that share the underlying concept of measured, appropriate care but differ substantially in what that care requires and what turns on it.
Historical Dictionary Support
The six shelf sources are in substantial agreement on the core structure: diligence is care or attentiveness, and law recognizes three degrees. Burrill cites Jones on Bailments for the proposition that care ranges across "infinite shades" before law reduces them to three — a formulation also adopted verbatim in both editions of Black's and in Rapalje & Lawrence, suggesting a common treatise ancestry. Bouvier frames diligence as "the correlative of negligence" — a useful doctrinal pairing that captures the term's function as a positive standard against which negligence is measured. Anderson's entry adds the procedural dimension, specifying that what constitutes "due diligence" in a negligence action is a question for the jury, which reflects the standard's flexibility in application.
None of the shelf sources address the modern transactional meaning of due diligence, which developed primarily through securities regulation and corporate practice in the twentieth century. Researchers should not expect historical dictionary support for that usage and should consult modern secondary sources and regulatory materials instead.
Jurisdictional Note
The three-degree framework for diligence was more formally maintained in civil law jurisdictions and in early American treatise law than in modern common law courts. In contemporary American practice, most jurisdictions apply a unified reasonable-person standard and do not formally distinguish among degrees of diligence in most contexts. The Scots law procedural meaning of diligence has no American common law equivalent and is confined to Scottish and mixed civil-common law jurisdictions.
Encyclopedia Cross-Reference
Mergers and Acquisitions — Due Diligence and Representations and Warranties (The Law Mind Business Organizations & Corporate Law Encyclopedia)
IP Due Diligence in Mergers, Acquisitions, and Financing (The Law Mind Intellectual Property Encyclopedia)
Citizen Suits in Environmental Law — Standing, Notice, and Diligent Prosecution (The Law Mind Environmental & Energy Law Encyclopedia)