PHI 251
A valid argument:
(1) The conclusion follows from the premises.
(2) The premises conclusively support the conclusion.
(3) In every possible situation in which the premises are all true, the conclusion is
also true.
(4) It is impossible for the premises to be true with the conclusion false.
(5) If the premises were true, then the conclusion would be true.
A sound argument: The premises are true and the argument is valid.
Truth-functional connectives:
∇Ο∇ • Ο
TTT
TFF
FTF
FFF
Truth-functionally compound sentence: A compound sentence whose truth-
value depends upon the truth-values of its constituent sentences and not on
anything else.
Truth-functional connective: a connective symbol or word that is used to make
truth-functionally compound sentences.
Conjunction symbol: •
