Scope Fallacy
Fallacies of Ambiguity
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Fallacy Name:
Scope Fallacy
Alternative Names:
None
Category:
Fallacy of Ambiguity
Explanation:
Scope Fallacies are a type of Amphiboly> which
can be common both in philosophy and in day-to-day discussions. Because it is a type
of Amphiboly, it relies upon ambiguities derived from grammar rather than the
definitions of words.
Examples and Discussion:
Unfortunately, the concept of "scope" in grammar is rather difficult to
understand. The examples on this page should, however, help clarify things. Let's
begin with this common proverb:
1. All that glitters is not gold.
Most people will understand what this is supposed to mean without noticing that there is a grammatical ambiguity in it. Where? It is created by the fact that the scope of the word "not" is unclear. This word could have either a narrow scope or a broad scope, creating in two possible meanings:
2. All that glitters is non-gold.
3. Not all of that which glitters is gold.
The first interpretation is a narrow scope, where the word "not" negates only the phrase "is gold." The second interpretation, which is what the saying actually means, is a broad scope. Here, the word "not" essentially negates the entire sentence. Of course, mere statements are not fallacies - only arguments can have fallacies. So, if we were to use the first and most literal interpetation, we could contruct this fallacious argument:
4. All that glitters is not gold. This rock glitters. Therefore, this rock is not gold.
It is necessary to understand that logical operators like "not" have a particular scope - which is to say, they affect some portion of the proposition in which they occur. Thus, the term "not" can affect some portion of the proposition or all of the proposition. Understanding what is affected is key to understanding the argument being made. You can read more about this fallacy, and specifically this example, at Gary N. Curtis' FallacyFiles.
An important way to understand such fallacies is to realize that, normally, whatever occurs in the second phrase is considered to be "in the scope of" the first phrase. Thus, "is not gold" falls under the scope or influence of "all that glitters." That is why statement #3 above is not fallacious - the "not" phrase occurs first, thus determining the scope of the rest of the sentence.
These examples should help to clarify things further:
5. I believe that for every person, there exists one true soul mate.
6. I believe there is one true soul mate for every person.
The first statement is not a problem, but the second one is. Certainly the speaker in the second case is trying to say that every person has "one true soul mate," but not necessarily the same soul mate for every single person. However, what is actually communicated is that there is indeed one person out there, somewhere, who serves as the true soul mate for absolutely everyone.
But if we change the statement to this:
7. There is somebody who has some soul mate.
Now we don't have a fallacy, because we have the same "some" with the same scope in both the first and second phrase.
Scope Fallacies aren't always so easy to pick out as in the above examples. In a common proof for the existence of a god, a scope fallacy is committed:
5. For every contingent being, there is a time when it does not exist. Therefore, there was a time when every contingent being did not exist. Because contingent beings cannot cause their own existence, their existence must have been caused by a necessary being - God.
The fallacy occurs in the first two sentences, with the scope of the idea of "does not exist." It might help to think of the first sentence as saying "All contingent beings do not exist at some point in time."
In the second sentence, is it assumed that the scope is so broad that, at some point in time, no contingent being could have existed. But this is not the necessary interpretation of the premise - it could be that some contingent beings have always been around, but that they keep changing.
Because it is easy to get confused with regards to the scope of some words, this sort of fallacy can be the most common form of amphiboly to cause people problems.
This is one of the reasons, actually, why you will see philosophical arguments represented by symbols instead of words and sentences. When used properly, the symbols won't create ambiguities like those in the examples here. Everything constrained by a symbol for "not" or "all" will be contained in parenthesis, much like you find in math.
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