Presentation for critical thinking classes on fallacies of vagueness: argument from the heap, conceptual slippery slope, fairness slippery slope, and causal slippery slope.

1. Chapter 13
Fallacies of Vagueness

2. Vague = imprecise
Unclear due to lack of precision
WokinghamLibraries CC0 Public Domain

3. Vague = imprecise
Unclear due to lack of precision
WokinghamLibraries CC0 Public Domain

4. Vague = imprecise
Unclear due to lack of precision
Imprecise
WokinghamLibraries CC0 Public Domain

5. “The man is bald.”
Not vague. He is clearly bald.
Helpaeatcontu CC0 Creative Commons Attribution-Share Alike 3.0 Unported

6. “The man is not bald.”Not vague. He is clearly NOT bald.
Airwolfhound Flicker

7. “The man is bald.”
He is neither clearly bald nor clearly not bald.
This is a borderline case.
ben-the-geek Flicker

8. Fallacies of Vagueness:
Exploit borderline cases in the use of
imprecise language like “bald”
Borderline Case
Clear Clear
ben-the-geek Flicker Airwolfhound FlickerHelpaeatcontu CC0 Creative Commons
Attribution-Share Alike 3.0 Unported

10. Vague Language is common
Borderline CaseClear Clear
Fast
Big
Rich
Long
Heavy
Easy
Slow
Small
Poor
Short
Light
Hard

11. Four Fallacies of Vagueness
1. Argument from the Heaps
Simon A. Eugster GNU Free Documentation License

12. Four Fallacies of Vagueness
2. Conceptual Slippery Slope
@CanStock Photo

13. Four Fallacies of Vagueness
3. Fairness Slippery Slope
Crimfants Flicker CC BY-SA 2.0

14. Four Fallacies of Vagueness
4. Causal Slippery Slope
GNU Free Documentation License

15. 1. Argument from the Heaps
Simon A. Eugster GNU Free Documentation License

16. Argument from the Heaps
eap of sand by adding one grain to an amount that i
Ivan Aleksic Flicker

17. Argument from the Heap
a heap of sand by adding one grain to an amount th
Peter Craven “Sand Stockpiles” CC BY 2.0

18. Argument from the Heap
eap of sand by adding one grain to an amount that i

19. Argument from the Heap
1) For any number, n, if someone with n dollars is
not rich, then someone with n + 1 dollars is not rich.
2) Someone with only one dollar is not rich.
3) If someone with only one dollar is not rich, then
someone with only two dollars is not rich.
4) Someone with only two dollars is not rich. (1, 2)
…and so on…
999,999,999) Some one with one hundred million
dollars is not rich (1, 999,999,998).

20. 2. Conceptual Slippery Slope
@CanStock Photo

21. Conceptual Slippery Slope
pposite end of a conceptual spectrum do not differ i
@CanStock Photo

22. Conceptual Slippery Slope
1) We should not draw a distinction between things
that are not significantly different.
2) If A is not significantly different from B, and B is not
significantly different from C, then A is not
significantly different from C.
Depends upon the following principles:

23. Conceptual Slippery Slope
ferent than a blastocyst, which is not much different
@CanStock Photo

24. 3. Fairness Slippery Slope
Crimfants Flicker CC BY-SA 2.0

25. Fairness Slippery Slope
ogic: Drawing a line between similar cases is unfair
binu kumar Flicker

26. Fairness Slippery Slope
Argues that drawing a line between
similar cases is unfair.
Yet we have to draw the line
somewhere.
Pass Fail
100 90 80 70 60 50 40 30 20 10 0
6059

27. Fairness Slippery SlopeYet…we have to draw the line somewhere.

28. 4. Causal Slippery Slope
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29. 4. Causal Slippery Slope
Logic: If A happens, that will lead to D, which is pure evil,
so we can’t allow A.

30. 4. Causal Slippery Slope
1. If gay marriage is legalized, then polygamy will be legalized.
2. If polygamy is legalized, then incest will be legalized.
3. If incest is legalized, then bestiality will be legalized.
4. If we legalize bestiality we are all going to hell.
5. We cannot legalize gay marriage. (1-4)
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31. 4. Causal Slippery SlopeThis is usually—though not always—a fallacious argument.
1. Are the effects really bad?
2. Are the effects likely to occur?
3. Do the dangers outweigh the benefits?
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32. What is a fallacy of vagueness?
WokinghamLibraries CC0 Public Domain

33. What is a fallacy of vagueness?
Imprecise
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34. What is an Argument from the
Heaps?
Ivan Aleksic Flicker

35. Argument from the Heaps:
Making a small change does not add up to a
qualitative difference.
E.g., adding a grain of sand to an amount
that is not a heap, will not make it a heap.
Ivan Aleksic Flicker

36. What is a
Conceptual Slippery Slope?
@CanStock Photo

37. Conceptual Slippery Slope:
Things that are at opposite ends of a conceptual
spectrum are the same. E.g., A is not much
different than B, which is not much different than
C, which is not much different than D, which is
not much different than E, so A is the same as E.
@CanStock Photo

38. Heaps or Slippery Slope?
“Brutus has a full bowl of food. Even if he eats a
piece of his food, it will still be full, so his bowl
of food will never be empty.”
Argument from
Heaps
Conceptual
Slippery SlopeNeither.
Ivan Aleksic Flicker
Sh4rp_i Dog Food 2 Flicker
@CanStock Photo

39. Good! It is an Argument from the
Heaps!
Ivan Aleksic Flicker

40. Argument from the Heaps: If it’s not empty,
taking away one piece of food won’t make it
empty!
Ivan Aleksic Flicker

41. What is a Fairness Slippery Slope?
Crimfants Flicker CC BY-SA 2.0

42. Fairness Slippery Slope:
w an arbitrary line to differentiate two things that are
binu kumar Flicker

43. What is a Causal Slippery Slope?
OpenIcons : CC0 Public Domain

44. 4. Causal Slippery Slope
If we allow X to happen, it will cause something bad to
happen, which will cause something worse to happen,
which will cause something evil to happen, so we can’t
allow X to happen.
OpenIcons : CC0 Public Domain

45. Heaps or Slippery Slope?
“Claire finished eating thirty minutes ago and I
finished twenty-six minutes ago. It’s almost the
same. Why can’t I swim now, too?”
Fairness Slippery
Slope
Causal
Slippery Slope
Neither.
binu kumar Flicker
OpenIcons : CC0 Public Domain
Michael Williams WikiMedia Commons

46. Yes! It’s a Fairness Slippery Slope.
Crimfants Flicker CC BY-SA 2.0

47. A Fairness Slippery Slope argues that drawing an
arbitrary line between two similar things is unfair.
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