Explanation
Disjunction connects propositions, properties, or courses of action through an or-relation. Formal logic distinguishes inclusive or, which permits both alternatives to be true, from exclusive or, which excludes simultaneity. Ordinary language often leaves context, stress, and world knowledge to determine the reading. A disjunction opens a space of possibilities but can also restrict it artificially when relevant alternatives are omitted. In argument, it therefore supports both clear case division and false dilemmas. The conceptual movement divides a situation into possible branches, examines their compatibility and completeness, and then leads either to a decision or to an enlargement of the initially proposed space.
Movement of thought
1. A question or proposition encounters several possible cases, actions, or truth conditions that require differentiation. 2. An or-expression connects the alternatives and initially determines which branches belong to the considered possibility space. 3. Context or formal definition determines whether several branches may hold together or exclude one another. 4. A counter-test asks whether the alternatives are exhaustive, genuinely incompatible, and formulated at the same logical level. 5. The decision space returns clarified or enlarged, as an overlooked third possibility may break open the initial disjunction.
Scientific use case
Logic, semantics, pragmatics, and argumentation analysis study truth conditions, scope, exclusivity implicatures, and false dilemmas. Experiments can test when hearers interpret linguistic or inclusively or exclusively.
Example
A form asks, “Notification by email or letter; both may be selected.” The addition explicitly establishes an inclusive reading and prevents users from assuming unnecessary exclusivity.
Counterexample
Someone claims, “Either you support my plan or you do not care about the project.” The possibilities are not exhaustive; opposition may arise from concern. The disjunction creates a false dilemma.
Distinction
Distinguish it from conjunction, alternative as an everyday term, exclusive either-or, dialysis, expeditio, and false dilemma. Specify inclusive or exclusive reading, scope, and exhaustiveness.
Effect on thought and perception
Disjunction structures alternatives and makes decisions analysable. An unclear or manipulatively narrow disjunction may hide possibilities, intensify polarisation, and replace reasoning.
Resonance
A sentence divides the road into directions. Only examination shows whether the branches exclude one another, can be travelled together, or conceal another path.
Etymology
Technical core term; individual etymological review pending
Provenance
Unresolved relation network → second core-concept review → Metzler/HWRh cross-check → ATLAS 239
Cite this entry
Reich, Michael (Hrsg./ed.): „Disjunction“. Atlas der Sprache, AT-CORE-239-011. ATLAS 260, data model 1.6.0. https://atlasoflanguage.com/concept/AT-CORE-239-011The address remains stable; editorial content may evolve. Editorial reading state: 2026-10-15. Include your access date for precise references.
Historical background
Mill explains the disjunction as a compound form that nevertheless makes one assertion about alternatives. From A or B it does not follow that either component is asserted separately. He analyses the form through conditionals: if one alternative fails, the other must hold. Logical evaluation therefore concerns the whole proposition rather than the isolated word or. The passage is not a complete modern semantics; inclusive and exclusive readings, modality and pragmatic restrictions on offers require additional analysis.
How conceptual history changes the analysis
Identify the alternatives, the operator's scope and whether context licenses at least one or exactly one option. The conjunction or by itself does not settle pragmatic exclusivity.
References for the historical section
- John Stuart Mill, A System of Logic, Ratiocinative and Inductive, eighth edition, New York: Harper & Brothers, 1882; Project Gutenberg ebook 27942 · Book I, Chapter IV, §3: compound, disjunctive and conditional propositions
Selected named passages read in the transcription. The title page identifies an 1882 printing of the eighth edition, not the first edition. No claim that these passages were present unchanged in the first edition; no first-attestation or exhaustive reception claim.