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Slippery Slope Fallacy

  1. May 11, 2010 #1
    I wasn't sure where to put this, as it is a question pertaining to logic, but not mathematical logic per ce.

    I don't understand why the slippery slope argument is considered a fallacy, especially in a political context.

    While it is obviously incorrect to say that some action inevitably leads to a consequence by means of a slippery slope, it does not seem incorrect to say that it can make such a consequence more likely. Incrementalism (the idea that the public will not tolerate large, sweeping changes but that smaller, incremental changes can lead to the same result without as much opposition) is an idea that has historically been used by political leaders, such as Ceasar Augustus. I was thinking about this in the context of the senator who recently proposed the biometric ID card as part ofd the immigration reform bill. He basically said that the public was ready for this because in today's society we are constantly made to show ID. It seems that if such a rule was passed (this bill specifically creates a biometric ID card that would be required as verification of empolyment elligibility) it does in fact make anothe rule (such as hypothetically that such cards could be a requirment for voting) more likely.

    This post is not about biometric ID, but about the notion of the slippery slope. It seems logical that in a case where a progressive series of changes have been tending in a general direction, but no individual change seems unreasonable given the current state of things, there becomes a necessity of "drawing the line" somewhere by pointing out the slippery slope.

    I understand the difference between "inevitably leads to" and "makes more likely" but can someone explain why this is considered a logical fallacy?
  2. jcsd
  3. May 11, 2010 #2
    Here's a quote from the wikipedia article that sounds like it answers your question.
  4. May 11, 2010 #3
    The wikipedia article confused me. It did not seem to make the distinction in there examples between "inevitably leads to" which is recognizable as incorrect, and "makes more likely."

    The cited gun ownership example does not make sense to me. Each of those arguments seem like they are valid.
  5. May 11, 2010 #4
    There are real slippery slope arguments that are not fallacious, it is when they are abused beyond reason that the fallacy emerges.
  6. May 11, 2010 #5


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    I think they're splitting hairs with the idea of a slippery slope fallacy. Different situations:

    1) Even though this looks like a small change, it makes some other change inevitable, which makes another change inevitable, and so on. This is the slippery slope argument used correctly.

    2) Technically, it's not the same as giving your opposition the one small change they need to get their foot in the door. (And the foot in the door concept is not a fallacy. If you get people to agree to one request, they are statistically more likely to agree to your next request.)

    3) It's definitely not the same as the argument that once you've moved a small way towards some end point, the likelihood of reaching the endpoint is greater. This is a valid argument, just not technically the slippery slope argument. (This argument is valid in football, as well. Surprisingly, if a team has the ball close to their own goal line, their opponent is more likely to achieve the next score even though they don't yet have the ball.)

    While many people do technically abuse the "slippery slope" argument, claiming a particular argument is a slippery slope fallacy is often a red herring. The person stating a particular change puts us on a slippery slope to X has made a mistatement even though their logic is valid for an entirely different reason (foot in the door syndrome, placing us in closer proximity, etc). The mistatement is trivial, but pointing out the mistaken terminology can derail the person from the point they were trying to make.
  7. May 11, 2010 #6

    Chi Meson

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    One of the fallacious assumptions of the "slippery slope" is that the slope is slippery at all.

    Each case needs to be appraised individually, but if a person or a society takes a step toward a condition that is considered to be "intolerable," then it is not correct to say that the next step will be easier. In some cases the next steps might be incrementally more difficult. It's sort of like "what if the "slope" is not downhill, but uphill?

    This would be the case if steps are taken that move away from the current point of social equilibrium. The health care issue is an example. Any additional step toward social medicine in this country is virtually impossible right now, isn't it? If anything, the next step will be backward.

    So one step toward a "condition" does not necessarily make arrival at that condition "more probable."
  8. May 11, 2010 #7
    This clarifies matters, thanks.
  9. May 11, 2010 #8


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    I think using "disrupting a stable equilibrium" argument or "disrupting an unstable equilibrium" argument provides more clarity than using the slippery slope argument.

    Being specific about which equilibrium condition currently exists makes it a vector argument instead of a scalar argument. It avoids a person claiming a "slippery slope" condition exists when they really mean a "spinning your tires" condition exists.

    Although, I have to admit that I've rarely, if ever, heard someone use a "slippery slope" argument to mean a stable equilibrium condition exists. But the equilibrium idea is still an appealling idea for aesthetic reasons, if nothing else.
  10. May 11, 2010 #9
    Yes, it does. The probability of a particular condition is still increased irregardless of increasing difficulty of steps. To go with the football analogy, the last few yards towards the endzone may be the hardest to gain, but being on the five yard line makes a touchdown more probable then being on the fifty.

    In the healthcare example, you are thinking of it as being the probability of another reform. You have to think of it as some hypothetical quantity of government involvement. When the HMO act was passed, for example, government becamed more involved in managing health care. The passage of this act made the total probability of arriving where we are today more likely.

    EDIT: I missed your use of the word necessarily as a qualifier. Given that, your statement is true. There are always exceptions to general trends.
  11. May 11, 2010 #10
    Perhaps you could elaborate how these physical examples translate to real world arguments that are used correctly and incorrectly. I am interested in this subject, and think it is one of the more difficult subtleties of logic.
  12. May 11, 2010 #11
    Another real life example: At the venue I work at it, we don't allow alcohol. But sometimes the owner will make an exception for an obviously older person. I always argue against this, because it has been my observation that allowing one person to drink will dramatically raise the probability of others drinking.
  13. May 11, 2010 #12
    On a slightly tangenital note, it is interesting how arguments that are techinally fallacious are often true. There is that argument whose latin name I can't remmeber, the one where you basically say, well this person is an idiot so whatever they say is likley to be idiotic. Although this is not a valid argument against an individual point, it does generally hold true. For example, I don't know for a fact what the position of the reverend Fred Phelps of the "God hates fags" church is towards the flooding of Nashville. It is perhaps possible that he has a sound physical explanation for it. But I would bet everything I had that his explanation is that it was an act of God unleashed as punishment for toleration of homosexuality. I understand the difference between evaluating an individual argument versus the likelihood of future arguments. But it does seem that people who have fundamentally nonsensical world views will produce non-sensical arguments.
  14. May 11, 2010 #13


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    Nudging a geosynchronous satellite out a gravity valley at 105 deg W longitude does not increase the probability of the satellite settling in the gravity valley on the opposite side of the Earth at 75 deg E longitude.

    Any nudging of the satellite from it's stable equilibrium point results in forces that send the satellite back towards its stable equilibrium point. At most, the range of variability has been extended just a bit.

    And while it's true that by nudging the satellite out of the gravity well, it will take less energy to permanently displace that satellite from the gravity valley, the amount of energy required to do it means the satellite will never settle into the opposite valley. The opposite valley is an impossible destination... in a single shot, anyway - it would take at least two separate phases: disrupt the current equilibrium; then conciously maneuver the satellite so that it would settle into the opposite equilibrium point.

    Socially or politically, this would be equivalent to tearing a law or policy down, clearing the way for a new law or policy to be created from scratch to fill the vacuum. Tearing down the old merely creates opportunity for new - it doesn't give any particular new any advantage.

    On the other hand, nudging a satellite off of a gravity bulge at 11.5 deg W longitude will result in the satellite drifting all the way to the opposite bulge at 162 deg E longitude, at which point it would only take a tiny nudge to balance the satellite over the opposite bulge.
    Last edited: May 11, 2010
  15. May 11, 2010 #14
    You could say the same for fieldgoals. But I've seen teams purposely lose some yards because they were too close and the kicker was better a little farther back.

    Like if you want to read a sign and you're too far away. Getting closer to the sign increases your chance of being able to read it, but if you walk up to it and stick your face right on the sign, you probably won't be able to read it.
  16. May 11, 2010 #15


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    And then there's the fallacy of using examples a lot more interesting than your main point. The reader goes off on a tangent, which is almost always a bad sine .... unless you're talking about small angle tangents and sines, of course. :rofl:
  17. May 11, 2010 #16


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    I often find the slippery slope argument used to create a strawman argument. That is, people use the slippery slope argument to equate a small change with the most extreme change in the same direction and then argue against the extreme case instead of the real proposed changes. For example, proposals that do anything to increase government oversight of the economy are often equated with communism and met with arguments why communism is bad (but not necessarily why the specific proposal is bad).

    This argument, however, is fallacious if you mischaracterize the endpoint. For example, consider proposals that desire to make America based more strongly on Christian values (e.g. restrictions on abortion). One could argue that such proposals would increase the probability of America becoming a fundamentalist theocracy (e.g. like a Christian version of Iran), but this argument is clearly mischaracterizes the intent of the proposal. In this case the desired endpoint is well short of a theocracy. Similarly, the desired endpoint of many proposals aimed at greater government oversight of the economy is well short of complete government control over the economy.
  18. May 11, 2010 #17
    This happens a lot, but it doesn't stop there. The usual sequence is cum hoc ergo propter hoc, followed by extended analogy, non causa pro causa, and converse accident / hasty generalization. From there it's a short step to ad-hominem, mental torture, physical abuse, and finally murder. This is what gives the slippery slope falacy such a bad name.
  19. May 11, 2010 #18
    :rofl: Excellent example.
  20. May 11, 2010 #19

    Chi Meson

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  21. May 11, 2010 #20
    I like Ogden Nash's comment,

    "You can't get there from here"
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