An Example of the Common Form of Moral Argument (worth 2 points) –
A Common Moral Form of Argument
- Vaughn presents an
argument in a specific form…
- (e.g. see page #51 in the
textbook, the argument about
Socrates).
- We will construct moral
arguments in that specific form in
order to justify moral judgments.
A Common Moral Form of Argument
- Vaughn points out that the
best way to defend one’s moral
judgment is to construct a sound
argument in which the moral
judgment is the conclusion of the
argument.
Soundness and Validity
- A sound argument is a valid
deductive argument with all true
premises.
- A valid argument is a deductive
argument in which the truth of the
premises guarantees the truth of
the conclusion.
Valid Arguments
- A valid argument does not have
to have true premises.
- A valid argument does not have
to have a true conclusion.
- But, a valid argument with all true
premises must have a true
conclusion.
Valid Arguments
- Validity describes a certain
relationship between the
premises and the conclusion of
an argument.
- That relationship is called
entailment.
- The premises entail the
conclusion.
Valid Arguments
- To say that the premises entail
the conclusion is simply to say
that if the premises were true,
then the conclusion would have
to be true.
- That can be the case even if the
premises are, in fact, false.
Valid Arguments - Test Questions:
True or False? A valid argument must have true premises…
TRUE?
FALSE?
Valid Arguments - Test Questions:
True or False? A valid argument must have true premises…
FALSE
Even though an argument is valid, it might have one or more false premises.
Valid Arguments - Test Questions:
True or False? A valid argument must have a true conclusion…
TRUE?
FALSE?
Valid Arguments - Test Questions:
True or False? A valid argument must have a true conclusion…
FALSE
Even though an argument is valid, if it has a false premise, it might have a false conclusion.
Valid Arguments - Test Questions:
True or False? A valid argument with all true premises must have a true conclusion…
TRUE?
FALSE?
Valid Arguments - Test Questions:
True or False? A valid argument with all true premises must have a true conclusion…
TRUE
A valid argument with all true premises MUST have a true conclusion.
Sound Arguments
- A sound argument is an argument
that is valid AND has all true
premises.
- A valid argument is unsound if it
has a false premise.
- An invalid argument is unsound
even if all of its premises are true.
Sound Arguments
- A sound argument must have a
true conclusion because it is valid
and has all true premises.
- Remember: a valid argument with
all true premises must have a true
conclusion.
Sound Arguments - Test Questions:
True or False? A sound argument must have true premises…
TRUE?
FALSE?
Sound Arguments - Test Questions:
True or False? A sound argument must have true premises…
TRUE
Having all true premises is one of the requirements of a sound argument.
Sound Arguments - Test Questions:
True or False? A sound argument must have a true conclusion…
TRUE?
FALSE?
Sound Arguments - Test Questions:
True or False? A sound argument must have a true conclusion…
TRUE
Because a sound argument is both valid and has all true premises, it must have a true conclusion.
Sound Arguments - Test Questions:
True or False? A sound argument must be valid…
TRUE?
FALSE?
Sound Arguments - Test Questions:
True or False? A sound argument must be valid…
TRUE
Being valid is one of the requirements of a sound argument.
Sound Arguments - Test Questions:
True or False? A valid argument must be sound…
TRUE?
FALSE?
Sound Arguments - Test Questions:
True or False? A valid argument must be sound…
FALSE
If the valid argument has a false premise, it is unsound.
Sound Arguments - Test Questions:
True or False? A valid argument with all true premises must be sound…
TRUE?
FALSE?
Sound Arguments - Test Questions:
True or False? A valid argument with all true premises must be sound…
TRUE
That is the definition of a sound argument: a sound argument is VALID and has all TRUE premises.
Constructing a sound argument.
- A common moral form
of argument is a valid form.
- Any argument in the common moral
form must be valid.
- But just because an argument is
in the common moral
form, it does not have to be sound.
Constructing a sound argument.
- Vaughn claims that the best
way to justify a moral judgment is
to construct a sound argument in
which the moral judgment is the
conclusion of the argument.
- Since a sound argument must
have a true conclusion, if the
argument is sound, the moral
judgment must be true.
Constructing a sound argument.
- When constructing an argument,
by following the common moral
form, the argument will be valid.
- To insure that the argument is
sound, just be sure that the
premises are true.
A Common Moral Form of Argument
- The first premise of an argument
in a common moral
form is a moral principle.
- The second premise is an
alleged fact.
- The conclusion is a moral
judgment.
A Common Moral Form of Argument
- A close inspection of the common form of moral arguments reveals that the form is as follows:
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- Notice that there are three terms
(A, B, and X) and that each term
appears twice.
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- By replacing A with some
general type of behavior, and
B with some moral language…
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- …premise 1 becomes a moral
standard (or principle), e.g.
Killing people is morally wrong.
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- Now, in premise 2, replace X
with some specific issue and A
with the same general behavior…
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- …and premise two becomes an
alleged fact, e.g. The Columbine
tragedy involved killing people.
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- …and the conclusion becomes a
moral judgment, e.g. The Columbine
tragedy was morally wrong.
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- This sample argument:
P1: Killing people is morally wrong.
P2: The Colombine trajedy involved
killing people.
__________________________________________________
∴ The Colombine trajedy is
morally wrong.
has an non-controversial conclusion.
A Common Moral Form of Argument
- But it demonstrates the correct form:
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- Notice the three terms (A, B, and X):
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- Each term appears twice, and in just
the right locations:
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- By following this form, the argument is
sure to be valid.
P1: All A’s are B’s.
P2: X is an A.
__________________________________________________
∴ X is a B.
A Common Moral Form of Argument
- To insure a sound argument, just be
sure that the premises of the argument
are true .
- Since a sound argument must have a
true conclusion…
- the moral judgment (which is the
conclusion) must be true!
A Common Moral Form of Argument
- Those who disagree with the moral
judgment must show that the argument
is unsound.
- An unsound argument is either invalid
or has a false premise.
- Since the argument is in a valid form, it is valid.
- Thus those who disagree with the
moral judgment must try to show a
premise is false.
A Common Moral Form of Argument
- To defend your argument (and your
conclusion/moral judgment):
- you point out that it is a valid argument,
- and then you must defend your factual
claim (premise two),
- and you must defend your moral
principle (premise one).