Vocabulary Flashcards
When is an argument valid?
An argument is said to be valid if it’s conclusion flows from it’s premises, and invalid if it doesn’t follow.
What is an argument?
A sequence of sentences of which one (the conclusion) follows from the other sentences (the premises)
Premises
When is an argument sound?
When an argument is VALID and in addition ALL it’s premises are TRUE, it is sound.
What is a sentential variable?
Small letters from the middle of the alphabet (p, q, r, s) that stand in for any arbitrarily selected sentence.
What is a sentence form?
Expressions like “p v q” that are employed to represent indiscriminately ALL sentences of the form depicted.
What is a conjunction?
A sentence of the form
‘p & q’
that is TRUE IF AND ONLY IF BOTH CONJUNCTS ARE TRUE and otherwise false.
What is a disjunction?
A sentence of the form
‘p v q’
that is TRUE IF AND ONLY IF AT LEAST ONE of its disjuncts are TRUE and false otherwise.
What is a negation?
A sentence of the form
‘~p’
that is TRUE IF AND ONLY IF it’s COMPONENT IS FALSE and FALSE if its COMPONENT IS TRUE
What is a material conditional?
A compound sentence of the form
‘p ⊃ q’
Whose antecedent is ‘p’ and consequent is ‘q’ typically of the form “If…then” which is FALSE IF AND ONLY IF p is TRUE and q FALSE, and TRUE OTHERWISE
What is truth-value?
The truth or falsity of a sentence.
What is a material biconditional?
A compound sentence of the form
‘p ≡ q’
that is TRUE WHEN IT’S COMPONENTS HAVE THE SAME TRUTH-VALUE and FALSE WHEN ITS COMPONENTS DIFFER IN TRUTH-VALUE
