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Argument from Definition

Also Known As: definitional argument argument from meaning semantic argument
Argumentation Scheme ID: argument_from_definition

Definition

The argument from definition asserts that something must have certain properties because of how the relevant term is defined. If X is defined as having property P, and the subject is classified as X, then it must have property P. This scheme is powerful in formal and legal contexts where definitions carry institutional authority. It becomes problematic when definitions are contested, when they are stipulated to win an argument, or when the real-world phenomenon does not neatly fit the definitional boundaries.

Examples

Marriage is defined as a union between a man and a woman. Same-sex couples are not a man and a woman. Therefore, same-sex couples cannot be married. This argument treats a particular definition as fixed and authoritative rather than as a social convention that can be revised.

A true sport requires significant physical exertion. Chess involves no physical exertion. Therefore, by definition, chess is not a true sport. This argument depends entirely on accepting that particular definition of sport, which is itself contestable.

Journalism is defined as reporting facts impartially without personal opinion. This outlet regularly publishes editorials and opinion columns. Therefore, it is not, strictly speaking, journalism. This relies on a narrow definition that many in the field would dispute.

Verification Steps
Verification Steps
Binary yes/no questions that an AI must answer to detect a reasoning pattern in a text.
Each of the 452 aspects has verification steps — simple yes/no questions designed to systematically detect whether a pattern appears in a text. For ad hominem: "Does the argument attack a person rather than their claim?" For false dichotomy: "Are only two options presented when more exist?" This ensures consistent, reproducible analysis.

Binary (yes/no) questions an LLM must answer to identify this aspect:

  1. 1

    Is a definition of a key term being used as a premise?

    Type: binary
  2. 2

    Is the definition standard and widely accepted, or stipulated for this argument?

    Type: binary
  3. 3

    Does the conclusion follow only because of the particular definition chosen?

    Type: binary
  4. 4

    Would a different reasonable definition undermine the argument?

    Type: binary
Deep Dive
The expandable detail section on each aspect page with examples, psychology, and counter-strategies.
The Deep Dive section provides in-depth information about each aspect: a real-world example showing the pattern in action, an explanation of why it works psychologically, practical advice on how to counter it, alternative names, and links to related aspects.