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*A* form / statement:
Categorical Logic

**absurd** (*adj*): logically
impossible; contradictory.

**absurdity, reduction to:** (See "reduction
to absurdity")

**acceptable / acceptability:**
Basic Concepts

**active mood:**
Basic Concepts

*ad baculum*:
List of Fallacies

*ad hominem*:
List of Fallacies

*ad ignorantium*:
List of Fallacies

*ad misericordiam*:
List of Fallacies

*ad populum*:
List of Fallacies

*ad ridiculam*:
List of Fallacies

*ad verecundiam*:
List of Fallacies

**addition (of a disjunct):**
Symbolic Logic

**affirming the consequent:**
List of Fallacies

**affirming a disjunct:**
List of Fallacies

**agent:** (See "agent-patient relationship")

**agent-patient relationship:**
Basic Concepts

**alternate:**
Symbolic Logic; (See
"disjunct")

**ambiguity: **
Common Fallacies

**amphiboly****: **
List of Fallacies

**analogy:**
Basic Concepts

**AND, binary operator: **
Symbolic Logic

**antecedent****
(of a condition):**
Symbolic Logic

**appeal against the person (***ad hominem*):
List of
Fallacies

**appeal to belief: **
List of Fallacies

**appeal to common practice: **
List of Fallacies

**appeal to consequences of belief: **
List of Fallacies

**appeal to emotion: **
List of Fallacies

**appeal to fear or force (***ad baculum*):
List of
Fallacies

**appeal to the people (***ad populum*):
List of
Fallacies

**appeal to pity (***ad misericordiam*):
List of
Fallacies

**appeal to unreliable authority (***ad
verecundiam*):
List of Fallacies

**argument:**
Basic Concepts

**Aristotle's square of opposition:** (See
"square of opposition")

**association (mental process):**
Introduction

**association (of terms) / associative: **
Symbolic Logic

**assumption: **
Basic Concepts

**attribute **(*n*): a quality or
characteristic inherent in or ascribed to someone or something.

begging the question (*petitio principii*) / circular reasoning:
List of Fallacies

**belief:**
Introduction;
Basic Concepts

**bi-condition: **
Symbolic Logic

categorical logic (*n*):** **the field of logic dealing with
things or concepts as classified and grouped according to specific
attributes.

**category **(*n*): a group of things or
concepts which share a common attribute or group of attributes.

**cause** (*n*):** **something that
produces an effect**.**

**charity** (*n*): the practice of interpreting
an ambiguous line of reasoning in its most favorable light.

**charity, principle of:** (See "principle of
charity")

**circular reasoning:** (See "begging the
question")

**claim** (*n*) the idea asserted by a
statement; (*vt*) to make an assertion.

**cogent / cogency:**
Basic Concepts

**coherent / coherence:**
Basic Concepts

**common sense:**
Introduction;
Basic Concepts

**commutation (of terms) / commutative:**
Symbolic Logic

**complement** (*n*): the shorthand
representation of the negation of a categorical concept "X" as "non-X,"
*e.g.*, "All cats are non-dogs."

**complex question: **
List of Fallacies

**composition****: **
Common Fallacies;
List of Fallacies

**conclusion:**
Basic Concepts

**condition (conditional proposition)****:**
Symbolic Logic

**conjunct: **
Symbolic Logic

**conjunction:**
Symbolic Logic

**consequent (of a condition)****:**
Symbolic Logic

**consistent / consistency:**
Basic Concepts

**constructive dilemma:**
Symbolic Logic

**contingent **(*adj*): true only under
certain conditions.

**contradiction** (*n*): in logic, an
absurd situation in which the affirmation and the negation of the same
claim are found to be either both true or both false at the same time
and place.

**contradictory** (*adj*):
Categorical Logic

**contraposition:**
Symbolic Logic

**contrary:**
Categorical Logic

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**deduction / deductive:**
Basic Concepts

**DeMorgan's laws:**
Implication & Equivalence

**denying the antecedent: **
List of Fallacies

**diagram, Venn:** (See "Venn diagram")

**dichotomy:** a choice limited to two
opposing extremes, with no option of middle ground or compromise.

**dilemma:** a choice between two options (or
among a limited number of options).

**disjunct****:**
Symbolic Logic

**disjunction****:**
Symbolic Logic

**disjunctive syllogism:**
Symbolic Logic

**division****: **
Common Fallacies;
List of Fallacies

**double negation: **
Symbolic Logic

E form / statement: Categorical Logic

**effect:** something produced by a
cause.

**elenchus** (*n*): a dialectal method
of argumentation (used extensively by Socrates, and still much used in
courts of law) relying on a dialogue of related questions and responses
to identify associations and contradictions, thereby to discern a
consistent path of reasoning.

**empirical** (*adj*): derived from
observation or experiment (Compare to "rational").

**enthymeme** (*n*): an argument with a
premise or conclusion that is unstated, but is either implied or
presumed to be inferred by the audience.

**equivocation****: **
Common Fallacies;
List of Fallacies

**evidence:**
Basic Concepts

**exclusive OR (XOR):**
Symbolic Logic

fact:
Basic Concepts

**fairness** (*n*) the practice of
interpreting a line of reasoning with maximum fidelity to the intent of
the original.

**fairness****, principle of:** (See "principle of
fairness")

**fallacy / fallacious: **
Common Fallacies

**figure (of a syllogism):**
Categorical Syllogism

**form (of a statement): **
Categorical Logic

**formal error**:
List of Fallacies

**formal logic** (*n*): the field of logic having
to do with logical structure and function, as represented in abstract
notation.

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**gambler's fallacy: **
List of Fallacies

**genetic fallacy: **
List of Fallacies

**ground:**
Basic Concepts

**grouping of operations:**
Symbolic Logic

**hierarchy of operations:**
Symbolic Logic

**hypothesis** (*n*): a logical
conjecture stated in such a way that it can be tested in order to
discern whether it is actually true or false.

**hypothetical****
syllogism:** Symbolic Logic

I form / statement: Categorical Logic

**IF, binary operator****:**
Symbolic Logic

**IFF (IF AND ONLY IF), binary operator****:**
Symbolic Logic

**implication: **Symbolic
Logic; Categorical Logic

**imply** (*vt*):** **to demonstrate through reasoning
that an idea is probably or necessarily true.

**incoherence / incoherent:** See "coherent"

**induction / inductive:**
Basic Concepts

**infer:** to become aware through reasoning
that an idea is most probably or necessarily true**.**

**inference**:** **an idea which
can be inferred
from a line of reasoning.

**informal logic** (*n*): the fields of logic
primarily concerned with matters other than structure and function.

**interpretation:**
Basic Concepts

**invalid / invalidity:** (See "valid")

**irrelevant / irrelevance:** (See
"relevant")

**irrelevant premise: **
Common Fallacies

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**judgment** (*n*): the outcome of an
evaluation.

knowledge: Introduction

linkage:
Basic Concepts

**logic** (*n*): a methodical system of
reasoning that relies on rational relationships among ideas to draw
reliable inferences.

**logical operator****:**
Symbolic Logic

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**major premise:**
Categorical Logic

**major term****:**
Categorical Logic

**middle term****:**
Categorical Logic

**minor premise****:**
Categorical Logic

**minor term****:**
Categorical Logic

**modus ponens****:**
Symbolic Logic

**modus tollens: **
Symbolic Logic

**mood (of a sentence): **
Basic Concepts;** (of a
syllogism):** Categorical Logic

**multiple negation **(See "double negation")

necessarily false (*adj*): logically incapable of being true
under any circumstances, e.g. "A triangle has four angles."

**necessarily true** (*adj*): logically
incapable of being false under any circumstances, e.g., "A triangle is a
polygon with exactly three sides and three angles."

**negation****:**
Symbolic Logic

**negation of operations:**
Symbolic Logic

*non sequitur*:
List of Fallacies

**NOT, unary operator****:**
Symbolic Logic

**notation:**
Symbolic Logic

O form / statement: Categorical Logic

**Ockham's razor:** as applied to logic, a
maxim that, of all consistent and coherent explanations that adequately
explain an idea without being in conflict with evidence, the simplest is most
likely to be true.

**operand: **
Symbolic Logic

**operations, hierarchy of:** (See "hierarchy
of operations")

**operator, logical****:**
Symbolic Logic

**OR, binary operator****:**
Symbolic Logic

**OR, inclusive and exclusive senses of:**
Symbolic Logic

**ordering of operations:**
(Symbolic Logic)

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**particular**** statement: **
Categorical Logic

**passive mood:**
Basic Concepts

**patient:** (See "agent-patient
relationship")

*petitio principii*:
List of Fallacies

*post hoc ergo propter hoc*:
List of Fallacies

**predicate (of a sentence):**
Basic Concepts

**predicate logic** (*n*): the field of
logic dealing with symbolic representation of categorical terms and
statements.

**predicate term: **
Categorical Logic

**premise:**
Basic Concepts

**principle of charity:**
Basic Concepts

**principle of fairness:**
Basic Concepts

**proposition **(*n*): a statement, so
called because it proposes that some idea is true.

**proposition logic:** (*n*): the branch
of symbolic logic that studies an abstract representation of a deductive
argument by substituting a letter of the alphabet for each of its
statements. Symbolic Logic

quantifier (*n*): a word indicating whether a categorical
statement applies to ALL, SOME, or NO members of a group named by the
associated term.** **

**question-begging:** (See "begging the
question")

rational (*adj*): lucid; logical; derived from logical
reasoning (Compare to "empirical").

**reason / reasoning: **
Basic Concepts

**reasoning, circular:** (See "begging the
question")

**reasoning, deductive:** (See "deduction")

**reasoning, fallacious:** (See "fallacy").

**reasoning, inductive:** (See "induction")

**red herring:**
List of Fallacies

**reduction to absurdity / ***reductio ad
absurdum*: a strategy of logical reasoning which shows an
assumption to be false by demonstrating that assuming it to be true
inevitably leads to a contradiction.

**reification****: **
List of Fallacies

**relevant / relevance:**
Basic Concepts

**rhetoric: **
Basic Concepts

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**simplification:**
Symbolic Logic

**sorites** (*n*): a series of "chained"
categorical premises which leads to a conclusion about the first and
last terms.

**sound / soundness (of an argument):**
Basic Concepts

**square of opposition:**
Categorical Logic

**statement:**
Basic Concepts

**statement logic:** (See "proposition
logic")

**straw man:**
List of Fallacies

**strong / strength:**
Basic Concepts

**stylistic variant:**
Categorical Logic

**subcontrary:**
Categorical Logic

**subject (of a sentence):**
Basic Concepts

**subject term:**
Categorical Logic

**sufficient / sufficiency:**
Basic Concepts

**syllogism: **
Categorical Logic

**syllogism, categorical:** (See "categorical
syllogism")

**syllogism, disjunctive:** (See "disjunctive
syllogism")

**syllogism, hypothetical:** (See
"hypothetical syllogism")

**symbolic logic:** (*n*): a field of
logic dealing with logical structure and function as studied in the
abstract by means of symbolic notation; symbolic logic includes
subfields of proposition logic, predicate logic;
Symbolic Logic

tautology (*n*): a claim that is true regardless of the truth
values of its component statements.

**term (of a syllogism): **
Categorical Logic

**truth:**
Basic Concepts

**truth, necessary: **(See necessary truth)

**truth table****:**
Symbolic Logic

**truth value:**
Basic Concepts

uncogent: (See "cogent")

**undistributed middle term:**
List of Fallacies

**universal statement: **
Categorical Logic

**unsound:** (See "sound")

**unwarranted assumption: **
Fallacies

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**valid / validity:**
Basic Concepts

**Venn diagram:**
Categorical Logic

warrant:
Basic Concepts

**weak / weakness (of an argument):** (See "strength")

**XOR:** (See "exclusive OR")

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**" (ALL):**
universal quantifier symbol.

**$ (SOME):**
existential quantifier symbol.

**^ (FALSE):**
truth-value=not-true symbol.

**∙ / * / &
(AND):** conjunction operator symbols;
Symbolic Logic

**→ / É
(IF):** condition operator symbols;
Symbolic Logic

**↔ / ≡ (IFF
/ IF AND ONLY IF):** bi-condition operator symbols;
Symbolic Logic

**~ /
(NOT):** negation operator symbols;
Symbolic Logic

**Ú (OR
[inclusive]):** disjunction operator symbol;
Symbolic Logic

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