Validity Flashcards
(20 cards)
What is a proposition?
A proposition is something that can be true or false.
What is a contradiction?
A proposition that cannot be true.
What is an argument?
A set of propositions (the premises) that someone uses to prove that another proposition (the conclusion) is true.
Can a proposition be valid?
No. A single proposition cannot be valid. Only an argument (a bunch of propositions) can be valid.
An argument is valid if its __________ follow from it premises
Conclusion
If an argument is valid then its conclusion must be true if ___________
its premises are true.
If valid argument has a false conclusion then _________
At least one of its premises must be false.
An argument is sound if _______
It is valid and all of its premises are true.
If and argument is valid but unsound then _______
At least one of its premises must be false.
What is the smallest number of propositions you need to make an argument?
Two. One premise, One conclusion.
A valid argument can have false premises and a false conclusion. (T/F)
True
A valid argument can have a true conclusion and false premises? (T/F)
True
A valid argument can have true premises and a false conclusion? (T/F)
False
A sound argument can have true premises and a false conclusion.
False
All __________ arguments are valid but not all valid arguments are __________.
Sound
If the conclusion of a valid argument is a contradiction then the argument cannot be ________.
Sound (note: it could be valid if the premises are contradictory)
If an argument is unsound then________
Either it is invalid OR at least one of its premises is false.
If an argument’s conclusion follows from its premises then the argument is _________
valid.
If an argument has true premises and a false conclusion then the argument must be_____
Invalid
An argument can be _______ and unsound but it cannot be sound and _________.
valid
