Informall fallacy: Non-sequitur

From the Latin, "it does not follow"

Examples and Observations:

·         "Non sequiturs are most obvious when absurd. For instance, from the facts that most cats like milk and some cats have tails I could not derive the conclusion that David Hume was the greatest British philosopher. That would be a complete non sequitur that borders on the surreal, whether or not its conclusion is true. Non sequiturs are often advertised by the spurious use of 'so' and 'therefore' . . ., but the context of a statement can also suggest that it is a conclusion derived from what has gone before even when there is no such word used to indicate it.

"Any formal fallacy will have a non sequitur as its conclusion, though most of these non sequiturs will be less obvious than the one above."
(Nigel Warburton, Thinking from A to Z. Routledge, 1996)

 

·         "The difference between the post hoc and the non sequitur fallacies is that, whereas the post hoc fallacy is due to lack of a causal connection, in the non sequitur fallacy, the error is due to lack of a logical connection."
(Mabel Lewis Sahakian, Ideas of the Great Philosophers. Barnes & Noble, 1993)

 

·         Ralph Wiggum: Martin Luther King had a dream. Dreams are where Elmo and Toy Story had a party and I was invited. Yay! My turn is over!
Principal Skinner: One of your best, Ralphie.
("The Color Yellow," The Simpsons, 2010)

 

·         "A non sequitur is any pretended jump in logic that doesn't work cleanly, perhaps because of unfounded premises, unmentioned complicating factors, or alternative explanations, such as 'This war is righteous because we are French!' or 'You will do what I say because you are my wife!'"
(Steve Hindes, Think for Yourself. Fulcrum, 2005)

 

·         Ralph Wiggum: Um, Miss Hoover? There's a dog in the vent.
Miss Hoover: Ralph, remember the time you said Snagglepuss was outside?
Ralph Wiggum: He was going to the bathroom.
("Sweet Seymour Skinner's Song," The Simpsons)

 

·         "Warming was caused by sunspots, or fluctuations in the Earth's orbit, or volcanic eruptions. Therefore it cannot be caused by mankind. The 'therefore' is the giveaway, the delicious non sequitur: just because Earth has warmed for one or another reason in the past is no reason why it cannot warm for a completely different reason in the future."
(John Llewellyn, "In a Confusing Climate." The Observer, Sep. 2, 2007)

Pronunciation: non SEK-wi-terr

thanks to:

http://grammar.about.com/od/mo/g/nonseqterm.htm

 

Affirming the Consequent

Definition:

Any argument of the following form is invalid:
If A then B
B
Therefore, A

Examples:

1. If I am in Calgary, then I am in Alberta. I am in Alberta, thus, I am in Calgary. (Of course, even though the premises are true, I might be in Edmonton, Alberta.)
2. If the mill were polluting the river then we would see an increase in fish deaths. And fish deaths have increased. Thus, the mill is polluting the river.

Proof:

Show that even though the premises are true, the conclusion could be false. In general, show that B might be a consequence of something other than A. For example, the fish deaths might be caused by pesticide run-off, and not the mill.

References

Barker: 69, Cedarblom and Paulsen: 24, Copi and Cohen: 241

Denying the Antecedent

Definition:
Any argument of the following form is invalid:
If A then B
Not A
Therefore, Not B
Examples:

1. if you get hit by a car when you are six then you will die young. But you were not hit by a car when you were six. Thus you will not die young. (Of course, you could be hit by a train at age seven, in which case you still die young.)
2. If I am in Calgary then I am in Alberta. I am not in Calgary, thus, I am not in Alberta.
Proof:

Show that even though the premises are true, the conclusion may be false. In particular, show that the consequence B may occur even though A does not occur.
References

Barker: 69, Cedarblom and Paulsen: 26, Copi and Cohen: 241

Inconsistency

Definition:
The author asserts more than one proposition such that the propositions cannot all be true. In such a case, the propositions may be contradictories or they may be contraries.
Examples:

1. Montreal is about 200 km from Ottawa, while Toronto is 400 km from Ottawa. Toronto is closer to Ottawa than Montreal.
2. John is taller than Jake, and Jake is taller than Fred, while Fred is taller than John.
Proof:

Assume that one of the statements is true, and then use it as a premise to show that one of the other statements is false.
References

Barker: 157

thanks to:

http://onegoodmove.org/fallacy/incon.htm



Missing the Point (Ignoration Elenchi)

An argument in defense of one conclusion instead proves a difference conclusion


1. Crimes of embezzlement have risen and theft of property the has risen dramatically. It follows therefore: that we should institute the dealth penalty as soon as possible.

(The premise may be true and we may agree with it, but it does not follow that the death penalty must be instituted because there are clearly better options on the table that can be legislated)

2. We should support the new housing bill for cheaper housing. We can't continue to see people living in the streets; homes should be cheaper for all.

(We can agree that people should not live on the streets and that homes should be for affordable, but we may not agree about the housing bill. It could have other caveats that are not related or have nothing to do with people living in the streets)

3. We should support affirmative action. White folks have run the country for too long to remember. They run most of government and private business today. You can't deny that this type of discrimination has existed and continues to exists.

(It is true that there is discrimination, but that affirmative action is the solution is that will end that discrimination is not true)



thanks to:

www.Hebrew4christians.com