Philosophy ch 8

Invalid argument form

An argument form is invalid if it is possible for an argument in that form to have all true premises and a false conclusion. Invalid argument forms that superficially resemble correct forms are called fallacious forms

Valid argument form

An argument form is valid if it is impossible for an argument in that form to have all true premises and a false conclusion.

Invalid argument

An argument is invalid if it is meant to be truth preserving but fails to meet the standards for deductive validity. An invalid argument is not an instance of any valid form of argument

Valid argument

An argument is valid if there are no circumstances under which it is possible for all of its premises to be true and its conclusion to be false. Valid is the term applied to correct deductive arguments, those that actually preserve truth rather than merely purport to preserve truth. Any instance of a valid argument form is a valid argument.

Conditional argument

An argument that contains at least one conditional sentence as a premiss

Disjunctive syllogism:

An argument that has the following form: p v q ~p over q

Deductive fallacy

An invalid argument that bears some resemblance, possibly misleading, to a (correct) deductive argument.

Logical equivalence:

Two sentences are logically equivalent if it is impossible for them to have different truth values. If two sentences are logically equivalent, then the statement of their material biconditional is a tautology

Truth-function connective

When components of a compound sentence are joined by truth-functional connectives, the truth or falsity of the compound sentence depends entirely on the truth or falsity of its component parts "If...then," when interpreted in the sense of a material conditional, is a truth-functional connective. Not is also a truth-functional connective. If a sentence p is true, then "Not p is false. If a sentence p is false, then "Not p" is true. In contrast, "If...then," in subjunctive counterfactual conditionals is not a truth-functional connective. The truth of a counterfactual conditional is not a function of the truth of its component parts.

Consequent

the sentence that depends on the stated condition

Antecedent

the sentence that states the condition

Self-contradiction

A compound English sentence is a self-contradiction if it is false by virtue of its logical structure, regardless of its content. A sentence form is a truth functional self-contradiction if its column in a truth table contains only Fs

Tautology:

A compound English sentence is a tautology if it is true by virtue of its truth function structure, regardless of its content. A sentence form is tautology if its column in a truth table contains only Ts

Conditional sentence

A compound sentence consisting of an antecedent and a consequent. The standard form of a conditional is :If (antecedent), then (consequent)" or "P yields q"

Material conditional

A conditional sentence in which the connection between the antecedent and the consequent is truth-functional rather than some "real" causal, definitional, or logical connection. A material conditional is false only when its antecedent is true and its consequent is false

Compound sentence

A sentence that contains another sentence as one of its parts