Ethics gives many college students a hard time. For some reason, professors fail miserably at giving students a quick and easy way to do proofs. Maybe it's because it's so easy that they are afraid philosophy and ethics will lose some of its mysticism if students know how easy it really is. Maybe it's because their brains are so complex that they cannot comprehend how to easily break it down for students. Maybe....
Really, who cares why. The fact is that doing ethical proofs are super easy if you follow 4 simple steps.
I'll review the basics first...
Valid
Arguments:
Modus ponens
If P, then Q.
P.
Therefore Q.
A pig (P) is an animal (Q).
Harry is a pig(P).
Therefore Harry is an animal (Q).
Modus tollens
If P, then Q.
Not Q.
Therefore Not P.
Example:
A pig (P) is an animal (Q).
Harry is not an animal (Q).
Therefore Harry is not a pig (P).
The most common Invalid
Arguments (also called "logical fallacies"):
Affirming the consequent
If P then Q.
Q.
Therefore P.
A pig (P) is an animal (Q).
Harry is an animal (Q).
Therefore Harry is a pig (P).
Denying the antecedent
If P then Q.
Not P.
Therefore Not Q.
A pig(P) is an animal (Q).
Harry is not a pig (P).
Therefore Harry is not an animal (Q).
***Don’t get
factually correct confused with valid or invalid. An argument can be factually correct and
still be invalid. An argument can be factually incorrect and still be
valid.
***To determine valid or invalid, the only thing that matters is whether
or not it fits into one of the valid argument formulas.
*** If an
argument if factually correct AND valid, then the argument is SOUND.
***These
formulas work regardless of whatever theory they are being applied to.
Steps for doing proofs:
1)
Before you start writing anything, on scratch
paper write out the 2 VALID logical arguments (modus ponens and modus tollens) and
label them.
2)
Label all the parts of the given argument with
Ps & Qs and underline all keywords (if, then, not and therefore.)
3)
In the margin or on scratch paper, write out the
given argument with only Ps, Qs and keywords.
4)
Does the argument match either of the two VALID
arguments?
Yes. Then it’s Valid.
No. Then it’s Invalid.
Example:
If I am President of the United States, then I can veto Congress.
I am not President.
Therefore, I cannot veto Congress.
STEP 1:
Write out the arguments.
Modus Ponens: If P,
then Q.
P.
Therefore Q.
Modus Tollens: If P, then Q.
Not Q.
Therefore not P.
STEP 2:
Label the parts of the argument (P) or (Q) and underline keywords.
If I am President (P) of the United States, then I can veto
Congress (Q).
I am not President (P).
Therefore, I cannot veto Congress (Q).
STEP 3: Write
out the sentence using only keywords, Ps & Qs.
If P, then Q.
NOT P
Therefore, NOT Q.
STEP 4: Does
it match either VALID argument formula above?
No. It is an INVALID argument.
(denying the antecedent)
That's it. Honestly. Give it a whirl. And it works every time...
That's it. Honestly. Give it a whirl. And it works every time...
