LogicalMANIPULATIVE

Definist Fallacy (Persuasive Definition)

What it is

Winning an argument at the definition stage: defining a contested term so that the desired conclusion follows from the definition alone, or so that the opponent's position is excluded by stipulation rather than by evidence.

How it works

Frankena (1939) coined “definist fallacy” for the error Moore had attacked — identifying one property with another by definition (good with pleasant) and then treating the identification as a discovery. In argumentative practice the more common form is Stevenson's (1938) persuasive definition: a word with a strong emotive charge (“freedom,” “theft,” “violence,” “person”) is given a new descriptive meaning while the charge is retained, so that whatever now falls under the definition inherits the approval or condemnation. The lever is that definitions are usually accepted as preliminaries — people wave them through to get to the argument, not noticing that the argument is already over. The honest version is a reasoner who sincerely thinks the term means what they say. The knowing version stipulates in order to smuggle: “taxation is theft” or “property is theft” turns a moral debate into a matter of vocabulary, and “true democracy” excludes inconvenient elections by fiat. The tell is a definition that would decide the dispute if accepted, offered as though it were neutral.

Real-world examples

  • •“Taxation is theft” (a libertarian slogan) and “property is theft” (Proudhon, 1840) are mirror-image persuasive definitions: each imports the condemnation of theft into a practice whose legitimacy is precisely what is being argued.
  • •Disputes over whether “racism” means individual prejudice or “prejudice plus institutional power” are often conducted as if settling the definition settled the substantive questions about discrimination, which it cannot; each side's preferred definition makes its own conclusion true by stipulation.
  • •In 2022, argument over the meaning of “recession” — whether two quarters of negative growth suffice, or whether the NBER's broader criteria apply — became a proxy for whether the U.S. economy was in one; the definition did the work an economic argument should have done, on both sides.
  • •A company defines “active user” as anyone who has opened the app in the last 90 days, so that a growth claim is true by definition; an investor who accepts the definition has accepted the claim.
  • •A jurisdiction defines “assault weapon” by listed features, and opponents argue that because the definition is arbitrary the category is meaningless — a definist move combined with the continuum fallacy.

Ethical guidelines

  • ●When a term is contested, flag your definition as a choice, say why you chose it, and argue the substantive question with the definition held fixed.
  • ●Do not define a term so that your conclusion follows from it; if it does, you have restated your position, not argued for it.
  • ●Be wary of keeping the emotional charge of a word while changing its descriptive content; that is the persuasive definition, and it works on you too.
  • ●Prefer defining by paradigm cases both sides accept over defining by stipulation that one side rejects.

How to defend against it

  • ►Ask whether the definition decides the dispute: “If I accept that definition, is there anything left to argue about?” If not, the definition is the argument and needs its own defense.
  • ►Separate the word from the question: “Call it whatever you like — is the practice justified?” This strips the emotive charge from the label and returns the discussion to the merits.
  • ►Offer an alternative definition with the opposite charge and ask which is correct; the speaker must then argue the substance.
  • ►Insist on paradigm cases: what clearly is X, what clearly is not, and where does the disputed case fall? Stipulation loses its grip once cases are on the table.
  • ►In commercial and technical contexts, ask for the operational definition behind any metric before evaluating the claim it supports.

From the Defense Playbook

Pin the Baileyminutes

When a position seems to change size depending on whether it is being advanced or defended, write down the bold version and the modest version side by side and ask which one is being claimed, so the speaker cannot enjoy the conclusions of one and the defensibility of the other.

Every playbook entry states how strong its evidence is and when not to use it. Browse the full playbook.

References

  1. Frankena, W. K. (1939). The naturalistic fallacy. Mind, 48(192), 464-477
    The coinage of “definist fallacy” and its analysis as identifying properties by definition.
  2. Stevenson, C. L. (1938). Persuasive definitions. Mind, 47(187), 331-350
    The concept of the persuasive definition: altering descriptive meaning while retaining emotive meaning.
  3. Copi, I. M., Cohen, C., & McMahon, K. (2011). Introduction to Logic (14th ed.). Pearson
    The textbook taxonomy of definitions (stipulative, lexical, precising, theoretical, persuasive) used to identify when a definition is doing argumentative work.
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