1 reply to this topic

[Dave]

ad hominem attack
This occurs when one attacks the person making the argument rather than the argument itself.
Example: "Ronald Muffinbottom believes that Lilliputians are prejudiced isolationists. But that can't be true because Ronald is a total moron who puts milk in his tea and I hate him."

Appeal to the people (argumentum ad populum)
Such arguments excite the emotions of a crowd or plays on a person's fears or desires to gain acceptance of the argument.
Example 1
Premise: Most people watch television.
Conclusion: You should watch television.

Example 2
Premise: If you drink Budweiser Beer, you will be rich, universally adored and ecstatically happy.
Conclusion: Drink Budweiser Beer to fulfill these dreams.

Begging the question
The term "begging the question" is itself commonly misused. It is a logical error caused when you assume the very claim you are attempting to prove (it is also called circular reasoning). It is NOT synonymous with "asking the question."
Example:
Premise 1: The Bible says that God exists.
Premise 2: The Bible can't be wrong because it is the divine word of God.
Conclusion: God exists.
The error in this argument is that we are assuming in premise 2 what we are trying to prove in the conclusion, namely, that God exists.


Attacking a Straw Man
This occurs when one distorts an opponent's argument in order to more easily attack it. The person attacks the distortion and then concludes that the opponent's argument has been defeated. In reality, only the distorted argument (the straw man) has been defeated, not the original argument.
Arguer 1: We shouldn't celebrate Columbus Day because Columbus came to America and killed and oppressed the natives.
Arguer 2: Pish posh! Plenty of people have come to America without killing or oppressing the natives. Therefore, we should continue to celebrate Columbus Day.
Analysis: Here, arguer 2 is twisting what arguer 1 said. Arguer 1 never said that EVERYbody who came to America killed and oppressed natives.

Ignorance of the Proof (ignoratio elenchi)
Also called: Missing the Point. The arguer ignores the logical implication of his/her own premises and draws a different conclusion entirely.
Example:
Premise: There is rampant abuse of the welfare system.
Conclusion: Therefore, our only alternative is to eliminate it altogether.
Analysis: The fact that there is abuse of the welfare system, it doesn't follow that the only alternative is to shut it down. The premise allows for the conclusion that there may be a method to eliminate the cheaters and abusers of welfare.

Equivocation
The meaning of a word is switched during the argument. Here's a painfully obvious example:
A plane is a carpenter's tool.
A fighter jet is a plane.
Therefore, a fighter jet is a carpenter's tool.

[Dave]

An argument is a set of sentences one of which (the conclusion) is said to be supported by the remaining sentences (the premises).

P1 All men are mortal.
P2 Socrates is a man.
C Socrates is mortal.

Premises: evidence for the truth of the conclusion
The conclusion is said to be implied by the premises.

Two types of arguments: deductive arguments and inductive arguments.
Deductive arguments claim that the conclusion is conclusively implied by the premises (i.e., if the premises are true, then the conclusion must be true).
Inductive arguments claim that the conclusion is probably true given the truth of the premises.

An argument is deductively valid if and only if it is not possible for the premises to be true and the conclusion false.
An argument is inductively strong if and only if the conclusion is probably true given the truth of the premises.
An argument is sound if and only if it is deductively valid and has true premises.

Deductive
P1 All humans are mortal.
P2 Socrates is a human.
C Socrates is mortal.
(This is a valid argument)

P1 All good students study.
P2 Joe studies.
C Joe is a good student.
(This is invalid)

P1 All men in this forum are left-handed.
P2 I am a man in this forum.
C I am left-handed.
(This is valid, but check the soundness of the premises. P1 is false.)

Inductive
P1 A million crows have been observed.
P2 All observed crows have been black.
C All crows are black.
An inductive argument makes a prediction: there is a high probability that all crows are black. This is not a good deductive argument. Check for the strength of the argument.

P1 90% of all website owners are drunks.
P2 Dave is a website owner.
C Dave is a drunk.
It’s good evidence, but it’s not conclusive evidence.


Another deductive argument:
P1 If Dave is a website owner then the moon is made of green cheese.
P2 Dave is a website owner.
C The moon is made of green cheese.
This is a valid argument but is not sound.


Necessary and Sufficient
Taking the test is necessary to pass the class,
but it is not sufficient to pass the class


Okay, hope I've bored you enough. Go post now.