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Slippery Slope

(also known as absurd extrapolation, thin edge of the wedge, camel's nose, domino fallacy)

Description: When a relatively insignificant first event is suggested to lead to a more significant event, which in turn leads to a more significant event, and so on, until some ultimate, significant event is reached, where the connection of each event is not only unwarranted but with each step it becomes more and more improbable.  Many events are usually present in this fallacy, but only two are actually required -- usually connected by “the next thing you know...”

Logical Form:

If A, then B, then C, ... then ultimately Z!

Example #1:

We cannot unlock our child from the closet because if we do, she will want to roam the house.  If we let her roam the house, she will want to roam the neighborhood.  If she roams the neighborhood, she will get picked up by a stranger in a van, who will sell her in a sex slavery ring in some other country.  Therefore, we should keep her locked up in the closet.

Explanation: In this example, it starts out with reasonable effects to the causes.  For example, yes, if the child is allowed to go free in her room, she would most likely want to roam the house -- 95% probability estimate[1].  Sure, if she roams the house, she will probably want the freedom of going outside, but not necessarily “roaming the neighborhood”, but let’s give that a probability of say 10%.  Now we start to get very improbable.  The chances of her getting picked up by a stranger (.05%) in a van (35%) to sell her into sex slavery (.07%) in another country (40%) is next to nothing when you do all the math:

.95 x .10 x .0005 x .35 x .0007 x .4 = about 1 in 25,000,000.

Morality and legality aside, is it really worth it to keep a child locked in a closet based on those odds?

Example #2:

If you accept that the story of Adam and Eve was figurative, then you will do the same for most of the Old Testament stories of similar literary styles.  Once you are there, the New Testament and the story of Jesus does not make sense, which will lead you to believe that the resurrection of Jesus was a “spiritual” one.  Once you accept that, you won’t be a Christian anymore; you will be a dirty atheist, then you will have no morals and start having sex with animals of a barnyard nature.  So you better take the story of Adam and Eve literally, before the phrase, “that chicken looks delicious”, takes on a whole new meaning.

Explanation: Accepting the story of Adam and Eve as figurative rarely (it is sad that I cannot confidently say “never”) leads to bestiality.

Exception: When a chain of events has an inevitable cause and effect relationship, as in a mathematical, logical, or physical certainty, it is not a fallacy.

Tip: The concept of a “bad day” is part of this fallacy.  You wake up in the morning, and you discover that you are out of coffee.  From there, you fallaciously reason that this means you will be grumpy, late for work, then behind all day in work, then have to stay late, then miss dinner with the family, then cause more friction at home, etc.  This is only true if you act it out as if it is true.  Of course, with an already bad attitude, you look back on the day, block out the good and wallow in the bad, just so you can tell yourself, that you were right all along about having a “bad day”.

Don’t let that happen.

References:

Walton, D. N. (1992). Slippery Slope Arguments. Clarendon Press.

[1] I am basing these estimates on my best guess... this is not meant to be an accurate study on child abduction, just an illustration of how odds work in the fallacy.



Registered User Comments

cu.inf
Wednesday, November 07, 2018 - 10:20:52 AM
There is a fallacy in the explanation of the first example. I'm setting aside whether it is okay to throw in estimated probabilities (which always fail to perfectly capture reality). The final probability was multiplied by 35% because the vehicle was described as a van, which is a nearly irrelevant detail. Further, it might be argued that the real concern might simply be that something will happen that's bad enough to outweigh the problems with keeping her in the closet, not that she will specifically be sold as a sex slave into another country. I'm fully aware that if I was using this to discredit the discrediting of the example, them I would be subject to the same criticism because I am focusing on the validity of the statistics rather than the point being made that the example has poor reasoning. A better way to explain the fallacy would simply be to point out that one can, for example, stop at the part of letting her roam the neighborhood or simply giving her proper education. The problem in a slippery slope fallacy is not so much that the events are unlikely, but that there are or can be things put in place that prevent those events from being a likely issue.

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Krista Neckles
Tuesday, July 10, 2018 - 04:06:07 PM
Hello Sir,

Could it be interpreted that the slippery slope fallacy is a formal fallacy? The way that this fallacy is structured reminds me of a flawed version of a hypothetical syllogism, in which someone says "If A then B. If B then C. Theefore if A then C".

Thank you Sir.

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Bo Bennett, PhD
Tuesday, July 10, 2018 - 04:27:05 PM
No, it would still be informal (inductive). Slippery slope mostly always implies probability rather than a certain, deterministic conclusion.

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Krista Neckles
Tuesday, July 10, 2018 - 05:01:37 PM
@Bo Bennett, PhD: Thank you Sir. But is there a fallacy that is an invalid form of the hyothetical syllogism?

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Bo Bennett, PhD
Wednesday, July 11, 2018 - 01:03:06 PM
@Krista Neckles: Not sure exactly what you mean. There are many deductive fallacies (listed on this site). These are mostly also invalid syllogisms.

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Krista Neckles
Wednesday, July 11, 2018 - 01:19:47 PM
@Bo Bennett, PhD: Hello Sir this is what I mean:

If P then Q
If Q then R
Therefore if P then R (This is a valid pure hypothetical syllogism)

This example is an invalid form:
If P then Q
If R then Q
Therefore if P then R

However I do not know what fallacy the invalid version is called. In the valid version there is a chain made while in the invalid version there is not. I hope I explained myself better.

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Bo Bennett, PhD
Wednesday, July 11, 2018 - 01:27:04 PM
@Krista Neckles: Off the top of my head I don't know either. Perhaps a non sequiter... general fallacy when something does not follow

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