Within Slippery Slope
Does a Blurry Line Mean No Line?
Blurred boundaries can make decisions harder, but they do not prove that every practical distinction is arbitrary.
On this page
- The heap problem and gradual change
- Usable thresholds without perfect precision
- How boundary blur gets misused
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Introduction
A common form of slippery slope reasoning begins with a genuine problem: many categories do not have perfectly sharp edges. There is no obvious grain of sand that turns a non-heap into a heap, no precise moment when someone becomes old, and no single millimetre that transforms a short person into a tall one. From this observation, some arguments make a further leap: if the boundary is unclear, then any distinction must be arbitrary, and once we accept one case we must eventually accept every neighbouring case as well. That leap is where a boundary problem can become a slippery slope claim. [stanford]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa… Encyclopedia of Philosophy
The key mistake is confusing vagueness with indistinguishability. A blurry border may make classification difficult at the margins, but it does not automatically erase meaningful differences across the entire range. Understanding how this transition occurs helps explain one of the most persistent forms of slippery slope reasoning in ethics, law, and public policy.
Does a Blurry Line Mean No Line?
The philosophical background is often called the Sorites paradox, from the Greek word for “heap”. The classic puzzle asks when a collection of grains becomes a heap. If one grain is not a heap, and adding a single grain cannot make the difference, then repeating that reasoning seems to imply that even a mountain of sand is not a heap. The paradox arises because ordinary language contains vague terms with borderline cases. [stanford]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa… Encyclopedia of Philosophy [Stanford Encyclopedia of Philosophy]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa…
This observation is important because many conceptual slippery slope arguments use the same structure. They proceed roughly as follows:
- There is no sharp boundary between case A and a slightly different case B.
- Therefore A and B must be treated identically.
- The same reasoning applies from B to C, from C to D, and so on.
- Eventually a very different case Z must also be treated identically.
The argument’s force comes from the fact that each individual step looks harmless. What is often overlooked is that the conclusion depends on chaining together many small similarities and treating them as if they eliminated all larger differences. Philosophers have long recognised the connection between sorites reasoning and certain slippery slope arguments. [Academia]academia.eduAcademiaThe Uses of Slippery Slope ArgumentIn this paper, I shall intend to show that the Sorites argument lies at the core of the Slippe… [PhilArchive]philarchive.orgPhilArchiveFUZZINESS AND THE SORITES PARADOXby M Vasconez · 2006 — kind of reasoning, then one embarks upon a slippery slope argument, wh…
The Heap Problem and Gradual Change
The heap paradox demonstrates a genuine intellectual difficulty. Many concepts are gradual rather than binary. Someone can become bald gradually. Colours blend into one another. Human development occurs across a continuum rather than through sudden transformations. [stanford]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa… Encyclopedia of Philosophy
Because change is gradual, it is often impossible to identify a single decisive transition point. Slippery slope arguments exploit this fact by suggesting that if no exact point exists, then no distinction can be justified.
Historically, however, philosophers have generally treated these as different questions:
- Question 1: Is there a perfectly precise boundary?
- Question 2: Can we still make useful distinctions?
The first question may have a negative answer. The second often has a positive one. A lack of perfect precision does not automatically make every classification worthless. [stanford]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa… Encyclopedia of Philosophy [Stanford Encyclopedia of Philosophy]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa…
For example, there may be difficult borderline cases between youth and adulthood. Yet that does not imply that a six-year-old and a thirty-year-old must be treated identically under the law. The existence of marginal cases does not eliminate obvious cases.
Why Practical Thresholds Still Work
Many institutions operate successfully despite fuzzy concepts. Legal systems, regulators, schools, and medical organisations routinely establish thresholds even when nature itself does not provide a sharp dividing line.
Age-based rules provide a clear illustration. Developmental research shows that different capacities mature at different rates, which is one reason legal systems often use different age thresholds for different activities rather than claiming that maturity appears at a single precise moment. [PMC]pmc.ncbi.nlm.nih.govPMCAdolescents' Cognitive Capacity Reaches Adult Levels Prior…by G Icenogle · 2019 · Cited by 347 — We argue it is therefore reasonabl…
The important point is not that these thresholds are perfect. It is that they are workable.
A voting age of eighteen, for example, does not imply that everyone becomes politically mature on their eighteenth birthday. Rather, it reflects a practical decision about where to draw a line in a continuous reality. Similar line-drawing occurs with driving ages, retirement ages, tax brackets, and countless administrative rules. [American Psychological Association]apa.orgissue 143American Psychological AssociationDrawing Legal Age Boundaries: A Tale of Two Maturities3 Jul 2019 — That said, age boundaries are in flu…
Legal and philosophical discussions of vagueness have long noted that societies often need determinate rules even when concepts contain grey areas. A rule can be justified because it provides consistency, predictability, and fairness, not because it captures a metaphysically perfect boundary. [Pure UVA]pure.uva.nlPure UVAThe slippery slope argumentby GA den Hartogh · Cited by 66 — Even so, arbitrary boundaries will be most acceptable, if they draw…
How Boundary Blur Gets Misused
The characteristic misuse occurs when an argument moves from “there is no perfectly sharp distinction” to “all distinctions must collapse.”
Several patterns are common.
Treating neighbouring cases as identical.
The argument assumes that because two adjacent cases are difficult to distinguish, they must receive exactly the same treatment. Repeating that move enough times creates the appearance that every case is equivalent to every other case.
Ignoring cumulative differences.
Even if each adjacent step is small, the total difference across many steps can be substantial. A person who is 150 cm tall and one who is 151 cm tall are very similar. A person who is 150 cm tall and one who is 210 cm tall are not. Similarity is not always transitive across long chains.
Assuming line-drawing is impossible.
The argument treats imperfect boundaries as evidence that no defensible boundary can exist. In practice, institutions routinely draw workable lines despite acknowledged grey areas. [Pure UVA]pure.uva.nlPure UVAThe slippery slope argumentby GA den Hartogh · Cited by 66 — Even so, arbitrary boundaries will be most acceptable, if they draw…
Converting uncertainty into inevitability.
The existence of difficult borderline cases becomes evidence that every future distinction will fail. This transforms a problem of classification into a prediction of unstoppable conceptual drift.
These moves are especially common in debates about ethics and public policy, where speakers argue that recognising one category will inevitably force recognition of increasingly distant categories. The strength of the argument depends not merely on the existence of a continuum, but on showing that later distinctions genuinely cannot be maintained.
When the Concern Is Legitimate
Not every boundary-based slippery slope argument is fallacious. [garyherstein.com]garyherstein.comSlippery Slope - THE QUANTUM of EXPLANATIONOct 13, 2016 — So, in a sense, slippery slope is going down the hill, while sorites is going u…
Sometimes a policy really does depend on a principle that becomes difficult to limit once accepted. In those cases, the challenge is not merely that the boundary is blurry but that there is no clear rationale for stopping at one point rather than another. Scholars of slippery slope arguments note that some versions raise legitimate questions about consistency and precedent rather than committing an outright fallacy. [PhilPapers]philpapers.orgPhil Papers This is the pre-peer reviewed version of the followingPhilPapersThis is the pre-peer reviewed version of the following…June 3, 2014 — by A Jefferson · 2014 · Cited by 38 — Slippery Slope A… [Informal Logic]informallogic.caInformal Logic The Basic Slippery Slope ArgumentInformal LogicThe Basic Slippery Slope Argument - Informal Logicby D Walton · 2015 · Cited by 67 — Cet article permet de résoudre ce prob…
The crucial difference is evidence.
A weak argument says:
There is no perfectly sharp line, therefore every distinction will collapse.
A stronger argument says:
There is no clear limiting principle, and here is why future decision-makers will struggle to justify stopping where you propose.
The second claim requires analysis of institutions, principles, incentives, and precedent. It cannot rest solely on the existence of a grey area.
The Practical Lesson
Boundary problems reveal a real feature of human concepts: many categories are vague, gradual, and resistant to perfectly precise definitions. The Sorites paradox shows why drawing lines can be intellectually difficult. [stanford]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa… Encyclopedia of Philosophy
What it does not show is that every line is meaningless.
The central error occurs when a genuine observation about vagueness is converted into a slippery slope claim. A blurry boundary may create hard cases at the margins, but it does not automatically eliminate the possibility of useful distinctions, practical thresholds, or principled stopping points. The existence of grey areas is evidence that line-drawing requires judgement, not proof that judgement is impossible. [Pure UVA]pure.uva.nlPure UVAThe slippery slope argumentby GA den Hartogh · Cited by 66 — Even so, arbitrary boundaries will be most acceptable, if they draw… [Stanford Encyclopedia of Philosophy]plato.stanford.eduEncyclopedia of Philosophy Sorites paradoxStanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa…
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Endnotes
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Source: plato.stanford.edu
Title: Encyclopedia of Philosophy Sorites paradox
Link: https://plato.stanford.edu/entries/sorites-paradox/Source snippet
Stanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophyby D Raffman · 1997 · Cited by 5 — The sorites pa...
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Link: https://plato.stanford.edu/archives/fall1997/entries/vagueness/Source snippet
Stanford Encyclopedia of PhilosophyVaguenessVagueness is standardly defined as the possession of borderline cases. For example, `tall' is...
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Title: Encyclopedia of Philosophy Sorites paradox
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Stanford Encyclopedia of PhilosophySorites paradox - Stanford Encyclopedia of Philosophy17 Jan 1997 — The sorites paradox is the name giv...
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Source: plato.stanford.edu
Title: sorites paradox
Link: https://plato.stanford.edu/archives/sum2005/entries/sorites-paradox/Source snippet
Stanford Encyclopedia of PhilosophySorites paradox30 July 2004 — The sorites paradox is the name given to a class of paradoxical argument...
Published: July 2004
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Source: academia.edu
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AcademiaThe Uses of Slippery Slope ArgumentIn this paper, I shall intend to show that the Sorites argument lies at the core of the Slippe...
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Link: https://philarchive.org/archive/VASFATSource snippet
PhilArchiveFUZZINESS AND THE SORITES PARADOXby M Vasconez · 2006 — kind of reasoning, then one embarks upon a slippery slope argument, wh...
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Source: plato.stanford.edu
Link: https://plato.stanford.edu/archives/spr2002/entries/vagueness/Source snippet
Stanford Encyclopedia of PhilosophyVaguenessFeb 22, 2002 — Vagueness is standardly defined as the possession of borderline cases. For exa...
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Source: pmc.ncbi.nlm.nih.gov
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PMCAdolescents' Cognitive Capacity Reaches Adult Levels Prior...by G Icenogle · 2019 · Cited by 347 — We argue it is therefore reasonabl...
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Source: pure.uva.nl
Link: https://pure.uva.nl/ws/files/1964247/28071_60._Slippery_Slope.pdfSource snippet
Pure UVAThe slippery slope argumentby GA den Hartogh · Cited by 66 — Even so, arbitrary boundaries will be most acceptable, if they draw...
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Title: Phil Papers This is the pre-peer reviewed version of the following
Link: https://philpapers.org/archive/JEFSSA.pdfSource snippet
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paradox - Stanford Encyclopedia of PhilosophyMar 26, 2018 — At least three conditions must be met for an argument to be an instance of th...
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paradox - Stanford Encyclopedia of PhilosophyJan 17, 1997 — The sorites paradox is the name given to a class of paradoxical arguments, al...
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Title: sorites paradox
Link: https://plato.stanford.edu/archives/win2003/entries/sorites-paradox/Source snippet
paradoxThis phenomenon at the heart of the paradoxes is now recognised as the phenomenon of vagueness. Once identified, vagueness can be...
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PHD THESISby M Călborean · 2020 · Cited by 1 — 55 Dominic Hyde and Diana Raffman, "Sorites Paradox", The Stanford Encyclopedia of Philoso...
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Title: Slippery Slope
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Can you outsmart the slippery slope fallacy? - Elizabeth Cox...
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Title: issue 143
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American Psychological AssociationDrawing Legal Age Boundaries: A Tale of Two Maturities3 Jul 2019 — That said, age boundaries are in flu...
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Informal LogicThe Basic Slippery Slope Argument - Informal Logicby D Walton · 2015 · Cited by 67 — Cet article permet de résoudre ce prob...
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Title: Sorites paradox
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Sorites paradoxThe paradox is to consider what happens when the process is repeated enough times that only one grain remains and if it...
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Slippery Slope - THE QUANTUM of EXPLANATIONOct 13, 2016 — So, in a sense, slippery slope is going down the hill, while sorites is going u...
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Title: slippery slope fallacy
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Definition & Examples14 Apr 2023 — The slippery slope fallacy is an argument that suggests an initial event will inevitably cause another...
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Philosophy of Vagueness: A Topological PerspectiveTo solve the Sorites paradox, then, subvaluationists contend that the argument is not v...
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[Mechanisms]({{ 'mechanisms/' | relative_url }}) of the Slippery Slopeby E Volokh — The analysis in this Article implicitly rebuts the argument that slippery slope arguments a...
Additional References
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Constitutional Law in an Age of ProportionalityI argue here for greater use of proportionality principles and doctrine; I also argue that...
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Concepts and Sorites ParadoxesThis new form of the sorites argument was called the subjectivist version. Consider, as above, predicate P...
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Title: implementation of the basel 3 1 standards near final policy statement part 2
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PS9/24 – Implementation of the Basel 3.1 standards near-...12 Sept 2024 — This Prudential Regulation Authority (PRA) near-final policy s...
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The article first delimits vagueness and ambiguity and sets it into relation...Read more...
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verses the onus of proof, so that rather than arguing about a particular...Read more...
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doesn't mean vagueness. It comes from Sorites, so it would...Read more...
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g a line between permissible and impermissible.Read more...
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1 The role of purpose in legislative interpretation19 Sept 2024 — This feature of interpretation is particularly strong in relation to st...
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PMCthe case of the slippery slope and the ad hominem argumentsby M Lillo-Unglaube · 2014 · Cited by 13 — The slippery slope argument is a...
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slope argumentsFull slippery slope argument A version of the slippery slope argument that combines various other versions in one complex...
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