A slippery slope is an argument that suggests that a certain initial action could lead to a chain of events with a relatively extreme result, or that if we treat one case a certain way then we will have to treat more extreme cases the same way too. For example, a slippery slope argument could involve saying that if we allow a relatively minor event to take place now, then a major and tragic event will happen in the near future as a result.
It’s important to understand slippery slopes, since they play a role in many situations, both in people’s internal reasoning process as well as in debates on various topics. As such, in the following article you will learn more about the various types of slippery slopes, understand when they’re fallacious and when they’re reasonable, and see how you can properly respond to people who use them.
Examples of slippery slopes
Slippery slope arguments are prevalent in many fields. For instance, the following is an example of a slippery slope argument in the context of bioethics:
“If we allow voluntary assisted suicide for terminal patients now, then in a few years it will become a commonplace way to get rid of unwanted people in order to reduce medical costs.”
“If we are willing to reduce the number of jurors from 12 to 10, then why not reduce it to just 2 people, 1 person, or none at all?”
Slippery slope arguments are also frequently used in politics, and especially by traditionalists, who oppose change and who want to argue against it in the media or in the legislative context. For example:
“If we increase the number of immigrants that we let into the country, we will eventually end up letting in anyone who wants to immigrate, and then the whole country will be destroyed.”
Types of slippery slopes
- Causal slopes, which revolve around the idea that a relatively minor initial action will lead to a relatively major final event.
- Precedential slopes, which revolve around the idea that treating a relatively minor issue a certain way now will lead to us treating a relatively major issue the same way later on.
- Conceptual slopes, which revolve around the idea that there is no meaningful difference between two things if it’s possible to get from one to the other through a series of small, nearly indistinguishable steps.
There is significant variation in terms of how different philosophers treat the different types of slippery slopes. However, in general, there are several characteristics that are shared between the different types and the different descriptions of slippery slope arguments:
- A start-point that is relatively mild.
- An end-point that is relatively extreme.
- A process of transitioning from the start-point to the end-point, usually without the ability to stop in the middle.
In the sections below, we will explore each of these types of slippery slopes in more detail.
Causal slippery slopes
A causal slippery slope is an argument that suggests that undertaking an initial action will lead to a chain of events that will culminate in a dramatic outcome. For example, a causal slippery slope could involve arguing that if we help students who struggle by providing them with extra tutoring, then eventually we will simply give perfect grades to all students regardless if they put in any effort or not.
As such, the basic structure of a causal slippery slope is the following:
“If we do [relatively minor thing] now, then it will cause [relatively major thing] to happen later.”
At least two events are necessary for a causal slippery slope, though any a number of events can appear in between them, with each event in the chain occurring directly as a result of the previous one. Accordingly, a causal slippery slope will usually have the following structure in practice:
“If we allow [minor event] to happen now, then [another minor event] might happen later, leading to [a medium event], and finally to the possibility that [major event] will occur.”
These slopes often involve a positive-feedback mechanism, where the initial action in question will set off a chain reaction that reinforces itself. This potential feedback mechanism can be mentioned explicitly by the person proposing the slope, or it can be an implicit part of their argument.
Note: the causal slippery slope is sometimes also referred to as a predictive slippery slope or an empirical slippery slope.
Precedential slippery slopes
A precedential slippery slope is an argument that suggests that if we set the precedent of treating something relatively minor a certain way now, then we will have to treat something relatively major the same way later on. For example, a precedential slippery slope could involve arguing that if we legalize a relatively harmless drug now, then we will also have to legalize a much more harmful drug later.
The basic structure of a precedential slippery slope is:
“If we treat [relatively minor thing now] a certain way now, then we will set a precedent which will force us to treat [relatively major thing] the same way later.”
As such, the precedential slippery slopes are based on the need to treat similar cases in a consistent manner.
Note: the precedential slippery slope is sometimes also referred to as the fallacy of slippery precedents, in cases where its use is fallacious.
Conceptual slippery slopes
A conceptual slippery slope is an argument that suggests that if it’s possible to transition between two things using a series of small, nearly indistinguishable steps, then there is no meaningful difference between those two things, and they must be treated the exact same way. For example, a conceptual slippery slope could involve arguing that if we allow euthanasia for animals, then there is no reason why we shouldn’t also allow it for people.
As such, the basic structure of a conceptual slippery slope is:
“Since it’s possible to get from [first thing] to [second thing] through a series of small steps, there is no valid way to draw a distinction between them.”
This argument is based on the concept of vagueness and on the sorites paradox (also known as the paradox of the heap). This paradox revolves around the fact that removing a single grain of sand from a heap of sand doesn’t turn it into a non-heap, but that, at the same time, a single remaining grain of sand won’t be considered a heap, which means that at some point, the act of removing sand turned the heap into a non-heap, despite the fact that there is no clear line of demarcation between the two. Accordingly, this type of slippery slope argument often uses language such as “where do you draw the line?”.
Furthermore, this type of slippery slope often involves gradualism or incrementalism, where people’s commitment to a certain concept or course of action is tied to a series of small, closely related steps. Specifically, this occurs when the slippery slope argument suggests that if you take an initial step, then there is no reason for you not to accept the next step, and the one after that, until you reach the final step, which is usually highly negative. As such, such arguments pressure you to either give up on your initial commitment, or to demonstrate that there is an inconsistency in your commitments.
Note: because of its association with the sorites paradox and the concept of assimilation, the conceptual slippery slope is sometimes referred to as a sorites slippery slope or as the slippery assimilation fallacy.
The slippery slope fallacy
Slippery slope arguments are often fallacious, though the reasons why they are fallacious can vary, and depend on the type of slippery slope which is being used.
When it comes to causal slippery slopes, a proposed slope is generally fallacious because it ignores or understates the uncertainty involved with getting from the start-point of the slope to its end-point.
This can happen, for instance, if the argument that presents the slope fails to acknowledge the fact that there’s only a small likelihood that the initial action being discussed will lead to the final event being predicted in the slope.
For example, consider the following formulation of a causal slippery slope:
“If we do [relatively minor thing] now, then [relatively major thing] will happen later.”
This slippery slope can be fallacious if there is only a small likelihood that doing the relatively minor thing now will lead to the relatively major thing later, since the argument fails to properly acknowledge this small likelihood.
When it comes to precedential slippery slopes, a proposed slope is generally fallacious because it ignores our ability to treat future cases differently than present cases, despite the precedent that the present cases set.
In this regard, precedential slippery slopes generally involve a false dichotomy, where only two options are presented (either refuse to set a certain precedent or set it and be forced us to treat other cases similarly in the future), while ignoring a third possibility, and namely the fact that we can set a precedent now, and still be able to treat other cases in a different manner in the future.
For example, consider the following formulation of a precedential slippery slope :
“If we legalize [relatively mild thing] now, then we will be forced to legalize [relatively negative thing] later.”
This slippery slope can be fallacious if it will be possible for us to avoid legalizing the [relatively negative thing] later, in spite of having set a certain precedent by legalizing the [relatively mild thing] in the present, since the argument fails to properly acknowledge this possibility.
When it comes to conceptual slippery slopes, a proposed slope is generally fallacious because it ignores the ability to differentiate between two things even if it’s possible to transition from one of them to the other using a series of small steps.
In general, this ability relies either on the fact that the small steps add up to create a significant difference, or on the fact that even in a series of small steps there can still be points where a differentiating line can be drawn for various reasons.
For example, consider the following formulation of a conceptual slippery slope :
“If you think that we should treat [relatively mild thing] this way, then you can’t justify not treating [related, relatively negative thing] the same way.”
This slippery slope can be fallacious if it’s possible for us to find a way to justify treating the [relatively negative thing] differently then we do the [relatively mild thing], despite the similarities between them, since the argument fails to properly acknowledge this possibility.
Logically sound slippery slopes
Slippery slope arguments are not inherently fallacious, and in some cases, a slippery slope argument can be a sound form of reasoning, rather than a logical fallacy. For example, the following is an example of a reasonable slippery slope argument:
“If we allow people to leave fires unattended anywhere in the forest, we will likely end up with a forest fire on our hands sometime in the future.”
This slippery slope argument suggests that if we allow something relatively minor to happen now (people leaving fires unattended anywhere in the forest), then a relatively major negative event will likely happen in the future (a forest fire), which is a reasonable stance to take in this case.
In general, whether or not a certain slippery slope argument is reasonable and logically sound depends on a number of factors, which in turn depend on the type of slippery slope argument that is used.
For example, when it comes to a causal slippery slope, the probability that the initial event will lead to the end event should be taken into account, since the more likely the end result is to occur, the stronger the slippery slope argument is. Accordingly, when slippery slopes are predictive in nature, their validity can be based on an assessment of the empirical evidence on the topic.
However, it’s important to note that this assessment will often be somewhat subjective, which means that even though it’s possible to quantify, to a degree, the likelihood of a certain chain of events, there is no definitive way to determine at what point this likelihood is so low that the argument in its favor becomes fallacious.
As such, while some slippery slopes are clearly reasonable, such as when they include a complete and definitive chain of events, and other slippery slopes are clearly fallacious, such as when there is no possible way to reach from the first event in the chain to the final one, the status of some slippery slopes is unclear and up for debate.
Finally, note that the way a slippery slope argument is phrased also affects its validity. For example, if there is a 50% chance that an initial event will lead to an end event, a slippery slope argument claiming that the initial event will “certainly” lead to the end event would be considered fallacious, while an argument which claims that the initial event “might” lead to the end event would be considered reasonable.
Rhetorical features of slippery slopes
Though people can use fallacious slippery slopes unintentionally, either during discussions or as part of their own reasoning process, fallacious slippery slope arguments are often used intentionally as rhetorical devices, since they can be quite persuasive when implemented correctly.
Slippery slope arguments that are used in this manner often involve extreme exaggeration, which evokes powerful emotions. Accordingly, slippery slopes are often combined with appeals to emotion, usually with the goal of appealing to negative emotions, such as fear or hate, but sometimes with the goal of appealing to positive emotions, such as hope or compassion.
Note that a slippery slope itself can lead either to a positive outcome or a negative one. When it leads to a positive outcome, a slippery slope can, for example, encourage people to undertake a certain course of action, with the promise of a major positive event in the end. Conversely, when a slippery slope leads to a negative outcome, it can, for example, encourage people to avoid undertaking a certain course of action, with the threat that if they do undertake that action, then it will lead to a major negative outcome for them in the end.
In general, slippery slopes are primarily associated with negative events, and as such, slippery slope arguments are frequently used as a fear-mongering technique. As part of this, slippery slope arguments often include a parade of horribles, which is a rhetorical device that involves mentioning a number of highly negative outcomes that will occur as a result of the initial event in question. Such arguments tend to follow specific patterns, such as saying that if a certain act is allowed in the present, then it will eventually lead to behavior that is similar to that of the Nazis.
Note: slippery slopes that are associated with a positive chain of events are sometimes referred to as representing a virtuous cycle, while slippery slopes that are associated with a negative chain of events are sometimes referred to as representing a vicious cycle.
How to respond to slippery slope arguments
There are various approaches that you can use when responding to a slippery slope argument:
- Point out the missing pieces of the slope. Slippery slope arguments often leave out important events that connect between the start and end points of the slope, and pointing these out can help illustrate the issues with the proposed slope.
- Highlight the disconnect between the different pieces of the slope. The more disconnected the pieces of the slope are from one another, the less reasonable the slope is; this can be an issue, for example, if there is a low likelihood that a certain event will lead to the one that’s supposed to follow it.
- Point out the distance between the start and end points of the slope. Demonstrating the distance between the start and end points of the slope helps illustrate why one is unlikely to lead to the other, and why it’s possible to justify treating the two in different ways.
- Show that it’s possible to stop the transition between the start and end points. Explain the ways in which it’s possible to actively prevent the initial event from leading to the end event, and possibly support this by using examples of previous cases where a similar method was used.
- Call out the problematic premises of the slippery slope argument. In some cases, one or more of the premises behind the slippery slope may be wrong, in which case you might benefit more from attacking the flawed premise directly, instead of addressing the issues with the slippery slope.
- Provide a relevant example that illustrates the issue with slippery slope arguments in general. This approach involves attacking the concept of slippery slope arguments in general, for example by showing that they can be made in a fallacious manner with regard to nearly any possible topic, though the way you do this should preferably be related to the topic of the slippery slope argument which is being discussed.
- Ask your opponent to justify the slope. If your opponent suggested a possible slope but didn’t provide any evidence which supports its validity, then you can remind them that the burden of proof rests with them, and ask them to justify why they believe that the slippery slope that they presented is reasonable.
You can use any combination of these approaches that you think will work well. When you do this, keep in mind that the effectiveness of each approach will vary based on a number of factors, such as the type of slippery slope which was used, the context in which it appeared, and the audience it was presented to.
In addition, another important thing to keep in mind when responding to a slippery slope is that slippery slope arguments are not inherently fallacious. As such, before attacking such an argument, you should make sure that it’s indeed fallacious. When in doubt, start by applying the principle of charity, and assume that the argument is not fallacious, as long as it’s reasonable for you to do so. If possible, ask the person who presented the slippery slope to explain their reasoning, which can be beneficial whether the slippery slope in question is fallacious or not.
Metaphors for slippery slopes
Various metaphors are frequently used in order to describe the concept of slippery slopes, and particularly the concept of causal slippery slopes. The most common metaphors used for this purpose are the following:
- Falling dominos. This metaphor represents the idea that an initial action will set off an unstoppable chain reaction. Because this metaphor is so prevalent, the slippery slope fallacy is sometimes also referred to as the domino fallacy.
- Thin edge of a wedge. This metaphor represents the idea that once a certain line is crossed, a quick chain of events will be set off.
- Bursting dam. This metaphor represents the idea that once a minor event occurs, an extreme and catastrophic outcome will occur as a result
- Camel’s nose. This metaphor refers to a tale where allowing a camel to put its nose in a tent led to the camel eventually coming inside entirely and refusing to leave.
- Growing snowball. This metaphor represents the idea that a minor initial event can escalate and reinforce itself, like a snowball rolling down the hill and gradually growing in size and picking up momentum.
- Butterfly effect. This metaphor refers to the idea that a minor initial action can lead to major, unforeseeable consequences down the road, as in a situation where a butterfly flapping its wings at one time ends up influencing the path of a tornado later on.
- Boiling frog. This refers to an apocryphal tale where a frog who is placed in water that is slowly being heated doesn’t notice the change until it becomes too late, because it is so gradual.
These metaphors often used together with slippery slope arguments, as analogies meant to illustrate the slippery slope being discussed.
Summary and conclusions
- A slippery slope is an argument that suggests that a certain initial action could lead to a chain of events with a relatively extreme result, or that if we treat one case a certain way then we will have to treat more extreme cases the same way too.
- There are different types of slippery slopes, but they all generally include three key elements: a start-point that is relatively mild, an end-point that is relatively extreme, and a process of transitioning from the start-point to the end-point, usually without the ability to stop in the middle.
- Slippery slope arguments can be either reasonable or fallacious; their validity depends on a number of factors, such as the likelihood that the initial event in question will lead to the proposed end result, and the phrasing used to convey this likelihood.
- You can respond to a fallacious slippery slope by attacking the proposed slope directly in a variety of ways, such as by pointing out missing pieces in the slope, highlighting the disconnect between the different pieces of the slope, pointing out the distance between the start and end points of the slope, or demonstrating that it’s possible to stop the transition between the start and end points of the slope.
- Other ways you can respond to a fallacious slippery slope argument include asking your opponent to justify the slope, giving a relevant example that illustrates the issues with such arguments in general, or attacking the problematic premises of the proposed slope if they are fallacious in some way.