Logical Fallacy 10: The Slippery Slope

The logical fallacy known as The Slippery Slope wrongly assumes that one thing must lead to another, and another and before you know it you get to something awful. Therefore you can't do the first thing. This is a very common fallacy. It's also known as the Fallacy of the Beard.

In an argument, it is the situation where acceptance of a minor detail of the opposing position will greatly weaken your position.

This is Part 10 in a series about Logical Fallacies. We are going through one fallacy at a time. There are many types of fallacious arguments. I’m going to try to explain them with examples then find ways to help you refute those arguments when they occur. Please comment or email if there’s a particular fallacy you want me to tackle, or if you have success with refuting an argument using a good technique you can share.

Formula:
  • If A happens, B will happen. If B happens, C, D, E, ... Z will happen! (oh noes!)
  • We don't want Z to happen.
  • Therefore A can't happen.
Example 1:
  • If I take aspirin, I'll start taking Oxycontin for headaches. If I take Oxycontin, I'll start buying it on the street. If I do that, I'll start looking for heroine to shoot up. If I start shooting up heroine, I'll get a dirty needle and get HIV, then die of AIDS....
  • I don't want to do heroine and die of AIDS.
  • Therefore I can't take anything for my headaches.
Of course this is not logical. For most people we have the ability to moderate and restrain ourselves to some degree. It is possible to stop after the first step and not go down the slippery slope.

Example 2:
  • Man: Will you have sex with me for a million dollars?
  • Woman: Sure!
  • Man: How about for ten dollars?
  • Woman: What kind of woman do you think I am?
  • Man: We've established that, now we're just arguing over price.

The woman has lost her argument over what seemed like a minor concession.

The Fallacy of the Beard term comes because what constitutes a beard? If you see a man and he has a beard, if he had one less whisker would it still be a beard? Two less? A thousand whiskers less? There is no clear cut line. Just because the difference between beard and no beard is vague (or bald versus hairy, etc), doesn't mean that there's no difference between the two. The difference is in degree. A big enough difference in degree can amount to a difference in kind.

How to Refute the Slippery Slope Fallacy?

My first suggestion is to state the fallacy and explain it. I think that's important in most circumstances. I think often people don't realize they are falling into fallacious arguments.

Once you've briefly explained it, I would recommend talking about moderation and how people every day all over the world restrain themselves thousands of times more often than not. Maybe even bring up how the person you're talking to has restrained themselves in some way recently, perhaps by restricting how much they ate or drank, etc (might not work if they are obese or an alcoholic, but you get my point). For instance, I really love coffee, but I only drank 2 cups for breakfast instead of the 5 I could have easily consumed.

Sources used:

8 comments:

  1. All true, of course. On the other hand, we don't want to lose sight of the fact that slopes are often slippery; or, at least, that it's usually easier to go down than up on one.

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  2. Had a friend who used to do this to rationalize her inability to get anything done, such as, housework...She said she would think of the consequences to the point where it would end up in something or someone dying. She would then be so paralyzed with fear she couldn't get anything started. Like vacuuming her apt because vacuuming could raise dust, which could set allergies in motion, which could lead to not being able to breathe, which would lead to passing out. So she wouldn't vacuum.

    My answer to her was that all things lead to dying anyway, so we can leave that out of the argument, and stay reasonable. Like if you vacuum, there will be Less dust to raise which will lead to easier breathing and no passing out.

    Like you say, Neece, it's all a matter of moderation.

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  3. I think your friend had a serious problem. Amazing how the mind rationalizes things and can go to such extremes.
    Yes, it's all about moderation, I think. :)

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  4. On the other hand, sometimes possible consequences are legitimate reasons for not doing something. For example, crossing a road without looking doesn't inevitably lead to death, but that doesn't mean that warning people to look both ways before crossing is illogical.

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  5. There is no slope in your example.

    Nor is the post talking about possible consequences. The problem with the slippery slope fallacy is that these "consequences" often don't exist and in reality are not even at all plausible.

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  6. The slippery slope is, to quote from the description at the top:
    "wrongly assumes that one thing must lead to another, and another and before you know it you get to something awful. Therefore you can’t do the first thing. "

    Now, crossing the road without looking might mean that you get hit by a fast-moving car, and getting hit by a car might mean a series of consequences in terms of energy transfer and human physiology that result in you dying. Therefore you shouldn't cross the road without looking (assuming that you don't want to die). Sounds to me like this meets the given slippery slope definition, I argue against doing the first thing, because it might possibly lead to a bad outcome. About the only possible point of difference is whether one thinks that the logical link between the consequences is valid or not.

    It may be that if we are talking about a quiet road most of the time you can safely cross it without looking, or to put it into your words "these 'consequences' often don't exist", does that mean that it's therefore a logical fallacy to look before crossing a quiet road, if you wish to avoid death and pain?

    For this reason, it seems to me that if someone makes a slippery slope argument that someone else disagrees with, that someone should point out the fallacy in the implied logical link, not just assert that the argument is invalid because it's a slippery slope.

    And you say that most slippery slope arguments have consequences that "in reality are not even at all plausible". How do you know this? Have you really tested a representative sample of slippery slope arguments and found that at least 51% of them are implausible? How are you defining what is implausible? Take for example the French Revolution, which was followed by the Napoleonic military dictatorship, and consequent death of much of the young men of France in war. Edmund Burke argued during the French Revolution that it was likely to collapse into a military dictatorship, and was much criticised at the time for such an implausible argument. A military dictatorship did indeed result, but how can you determine if Burke was right because his analysis was right, or he was right by pure chance? This strikes me as a question that rational people of good will could validly differ on, and it's not like we can conduct a controlled experiment on the question, nor on many important questions like it.

    Your assertion here that most slippery slopes have consequences that in reality are not even at all plausible strikes me as deeply subjective, rather than logically necessary. (I do not therefore conclude that most slippery slope arguments have consequences that in reality are at least plausible, I have an open mind on the question.)

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  7. Le sigh…

    No, a slippery slope requires just that, a slope. A chain of events that are claimed to be linked together without any causation. What you are giving, is a direct cause and effect. None of your examples are even slippery slope arguments, let alone slippery slope fallacies.

    I wasn’t joking when I said there is no slope in your argument. And you didn’t give any either. To claim the slippery slope fallacy is often accompanied exactly why it is such, which entails saying why the link doesn’t exist.

    If the causation and consequences did exist, it wouldn’t be a slippery slope fallacy. The reason why it’s called a fallacy, is just that, it’s not valid. Your argument using Edmund Burke is also not a slippery slope fallacy, regardless if he was right or wrong. There is no slope.

    You took the “consequences” part a bit out of context. First, I’m talking about slippery slope fallacies and not slippery slope arguments. Second, the reason why these consequences aren’t plausible is because correlation and causation leading up to those consequences are not explained. A slippery slope is a form of a non sequitur. This means that the conclusion does not necessarily follow the premises.

    This means if you give examples where the conclusion is following the premises, you are not giving an example of a slippery slope fallacy just by that alone… even ignoring the part about the use of a chain. A slippery slope argument isn’t even always fallacy.

    Taking this into consideration, I’m not even really sure what your point even is. So you can make an argument that isn’t a fallacy… well then we’re not talking about that argument.

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  8. Le sigh...

    No, a slippery slope requires just that, a slope. A chain of events that are claimed to be linked together without any causation. What you are giving, is a direct cause and effect. None of your example are even slippery slope arguments, let alone slippery slope fallacies.

    I wasn't joking when I said there is no slope in your argument. And you didn't give any either. To claim the slippery slope fallacy is often accompanied exactly why it is such, which entails saying why the link doesn't exist.

    If the causation and consequences did exist, it wouldn't be a slippery slope fallacy. The reason why it's called a fallacy, is just that, it's not valid. Your argument using Edmund Burke is also not a slippery slope fallacy, regardless if he was right or wrong. There is no slope.

    You took the "consequences" part a bit out of context. First, I'm talking about slippery slope fallacies and not slippery slope arguments. Second, the reason why these consequences aren't plausible is because correlation and causation leading up to those consequences are not explained. A slippery slope is a form of a non sequitur. These means that the conclusion does not necessarily follow the premises.

    This means if you give examples where the conclusion is following the premises, you are not giving an example of a slippery slope fallacy just by that alone... even ignoring the part about the use of a chain. A slippery slope argument isn't even always fallacy.

    Taking this into consideration, I'm not even really sure what your point even is. So you can make an argument that isn't a fallacy... well then we're not talking about that argument.

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