1. Critical Thinking Lecture 5b Fallacies in Reasoning (2)
By David Kelsey

2. Ad Hominem
An Ad Hominem fallacy is a kind of response to a claim that aims at the person making the claim, not the claim itself.
This is to think that some consideration about a person refutes the claims that he or she makes.
So the Ad Hominem mistake is to attack the man and not his position or argument.
A claim made by your strange English professor needn’t be strange.

3. Personal Attack Ad Hominem
A personal attack ad hominem claims that because someone has certain negative features it follows that a claim she makes is false.
Shortcomings in a person don’t entail shortcomings in her ideas or beliefs.
Just because someone uses profanity or has a tattoo or is a jerk doesn’t mean he must be saying something that is false.

4. Inconsistency Ad Hominem
An Inconsistency ad hominem claims that because what a person claims is inconsistent with something else she has said or done, it follows that her claim is false.
For example, you might reply to your friend Sam who has just bought into the idea of global warming: “Sam you now say you believe that global warming is real. Just last weak you laughed at the idea.”
Sam is allowed to change his mind…

5. Circumstantial Ad Hominem
A Circumstantial ad hominem is to hold that because a person’s circumstances are a certain way it follows that some claim she makes is false.
For example, imagine your priest gives you an argument against abortion and your response is to automatically dismiss the argument just because he must say such things.

6. Positive Ad Hominem
A Positive ad hominem is holding that the claim a person makes follows from some positive consideration about the person.
For example, just because Einstein was clever and smart it doesn’t follow that some claim he makes is clever or smart

7. Poisoning the Well
To poison the well is to perform an in advance ad hominem.
This occurs when one “poisons” someone’s mind about a third person.
These are often seen in rumors. One person spreads a rumor about a second person with the purpose of damaging his or her reputation.

8. Genetic Fallacy
When one tries to refute a claim based on its origin or history she has committed the genetic fallacy.
For example, one might try to refute the idea that God exists on the grounds that the belief in God first arose in very different times, times when people believed in magic and superstition.

9. Genetic Fallacy vs. Circumstantial Ad Hominem
The genetic fallacy and the circumstantial ad hominem are closely related.
Remember that to commit Genetic fallacy is to refute a claim by criticizing the origin or history of the claim.
And committing Circumstantial ad hominem is to refute a claim because of the circumstances or history of its author.

10. Straw Man
To commit the Straw man fallacy is to refute a claim or argument by distorting it or oversimplifying it or misrepresenting it in such a way that it can be easily refuted.
To reconfigure an opponent’s claim or argument so that it seems false or ridiculous.
For example, say your wife asks you to clean the attic today. You commit the straw man if your response is to say something like “What again? Do we have to clean it out every day?”
To knock down a straw man is to then show through argument that the reconfigured argument (or claim) is unsound (or false).

11. False Dilemma
A false dilemma limits considerations to a choice between only two alternatives although other reasonable alternatives are available.
A false dilemma will always neglect at least one quite reasonable and available alternative because it isn’t preferrable.

12. False dilemma examples
Say, for example, you tell your friend ‘hey this Friday night let’s either go to my favorite bar or we can go to the library to study’.
But of course no one wants to go to the library to study on a Friday night.
Or say you try to make this argument: Either you endorse prayer in public schools or your are an atheist. Since you don’t endorse prayer in public schools you must be an atheist.

13. Perfectionist fallacy
One commits the perfectionist fallacy if in considering some policy or claim she rejects it because it isn’t perfect.
This is a false dilemma because it says either the claim meets every one of our expectations or we reject it.
For example, you might argue that you shouldn’t quit smoking because quitting won’t make you live forever anyway.

14. Line Drawing Fallacy
The Line-Drawing fallacy occurs when one insists that a conceptual line must be drawn at a particular point when drawing such a line isn’t necessary.
To draw a conceptual line is to specify a rule that tells us the particular point, place or time at which a concept will be instantiated.
This fallacy is committed when you ask of a concept that it has a hard and fast line for its occurrence when the concept is vague and so doesn’t work like that.

15. An example of Line Drawing fallacy
Here is an example of the Line Drawing Fallacy:
One might claim that
1) it isn’t possible for a person who isn’t rich to become rich if we give her one dollar.
2) And it isn’t possible for her to be rich if we give her another dollar.
3) And she isn’t rich if we give her another…and another…and so on.
Thus, no matter how many dollars we give her she will not be rich.
Vague concepts: Such reasoning is fallacious because it attempts to make clear and precise the instantiation of vague concepts like rich, bald or excessive force.

16. Slippery Slope
The Slippery Slope fallacy occurs when one claims that one thing causes another when it isn’t reasonable to say so.
We commit this fallacy when we claim that a causal relation exists between two actions yet there is very little to no evidence in support.
For example, I might argue that if we require handguns be registered the next thing you know all guns will be illegal.
Examples in DirectTv commercials and other advertisements…

17. Misplacing the Burden of Proof
One commits this fallacy when she misplaces the burden of proof on the wrong side of an issue.
To understand this fallacy you must understand what it means to say that the burden of proof rests on a position.
Remember that for any issue there are two positions one can take on the issue.
For example, consider the issue Do ghosts exist? To this issue I can take the position that yes ghosts do exist or no they don’t.
When we have an issue like this there is a Burden of Proof, or a Burden To Prove that rests on one of the two positions available.
This fallacy is to place the burden on the wrong position, as a persuasive move, usually to try to win an argument.

18. The burden of proof
To say the burden of proof rests on a claim is to say that if one is to hold this position there is a burden to prove it which rests upon the person claiming it.
Looking back at our Ghost example, let’s say that the burden of proof rests on the position that Ghosts exist.
Of course if you hold the position that Ghosts do not exist you need to support this position with reasons, but you don’t owe any such justification until the other side has met the burden by providing enough good reason for thinking Ghosts do in fact exist.
So the position upon which the burden of proof rests must be supported first and foremost. Only then must the opposing position be supported.
Thus, there is a temporal priority to defend the position upon which the burden rests.

19. The burden rests on the least plausible position
The burden of proof will always be placed on whichever side of an issue is less plausible.
Something that isn’t plausible needs justification…
The burden, in general, ought to be placed on the affirmative side of an issue.
We generally want to hear reasons why something is the case before we hear why it isn’t the case.
Consider someone who believes Bigfoot is real.

20. The burden of proof in special circumstances
Under special circumstances the burden of proof is placed on a particular side of an issue.
In criminal court the burden of proof always rests upon the prosecution to prove the defendant is guilty beyond a reasonable doubt.
This is why we say that a defendant is innocent until proven guilty.

21. Begging the Question
One begs the question when one of the premises of her argument assumes the truth of the conclusion.
When begging the question one attempts to make an argument but some premise of her argument either rests upon the conclusion of the argument or it rests on the same dubious support that the conclusion rests upon.

22. Circular Reasoning
Begging the Question is sometimes called ‘Circular Reasoning’ just because when someone begs the question the premises of her argument really rest upon the conclusion for their truth and yet the conclusion is supposed to rest upon the premises for its truth.
Thus, there is a vicious circle created and the conclusion is really never justified by the independent reasons it needs.
For example, say I argue that God exists because it says so in the bible and everything in the bible has to be true because God inspired it of course.

23. Another example of begging the question
Imagine I define abortion as the murder of an innocent child.
Here I have also begged the question. This is to say that I have just assumed an answer to the central question at issue: is abortion wrong?
So I cannot define abortion in such a way as to assume the answer to the central debate behind abortion. I must offer proof and reasons for abortion being immoral, I cannot just define it so.