What fallacy is it to present proof of something that's similar to X, to conclude X?

Question

Consider the following argument for a claim X:

1. Present proof of statement X', which is similar to but different from X (and doesn‘t imply it).
2. Conclude that X holds.

Example:

1. Polls show that 80% of all people prefer strawberry over vanilla ice cream.
2. Conclusion: Nobody likes vanilla ice cream.

This is a fallacy, since it is perfectly possible to prefer something over something else, while liking both of these arbitrarily much.

Does this fallacy have a name?

Can this be classified as a straw man fallacy (even if you are not misrepresenting someone else's arguments)?

Answer 1

Here is Wikipedia's description of the straw man fallacy:

A straw man is a common form of argument and is an informal fallacy based on giving the impression of refuting an opponent's argument, while actually refuting an argument that was not presented by that opponent.

The example provided is

1. Nobody likes Vanilla Ice Cream.
2. Indeed polls show that 80% of all people prefer strawberry over vanilla ice cream.

Assuming the second statement is true, which seems doubtful, the problem with the first statement is that it might be too broad. If the second statement is true, then 20% do prefer vanilla ice cream and so claiming "nobody" does is inaccurate.

Bo Bennett has a couple pseudo-logical fallacies that might describe this situation better than "straw man argument":

Too Broad: The definition includes items which should not be included. This is more of an error of fact than reason.

Weasel Wording: Using ambiguous words in order to mislead or conceal a truth: “Save up to 50% or more!” This is more of a marketing gimmick than a fallacy.

The question is:

Can this be classified as a straw man fallacy (even if you are not misrepresenting someone else's arguments)?

Wikipedia further states:

This technique has been used throughout history in polemical debate, particularly in arguments about highly charged emotional issues where a fiery "battle" and the defeat of an "enemy" may be more valued than critical thinking or an understanding of both sides of the issue.

Without having an opponent to defeat there does not seem to be any point in calling the argument a straw man when other terms, such as "too broad" or "weasel wording", would be more descriptive even if they aren't considered more than "pseudo"-logical fallacies.

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Bennett, B. "Pseudo-Logical Fallacies" https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/6/Pseudo-Logical-Fallacies

"Strawman" Wikipedia https://en.wikipedia.org/wiki/Straw_man

Answer 2

This would appear to be just an invalid argument, as it takes the premises of a proof of X' (or the simple assertion of X') and asserts that they imply X, when it appears to be a premise of this question that they do not. One might call it a non-sequitur - a formal, logical or deductive fallacy - but to identify it as a more specific specific named fallacy, one would have to look into the reasons why its proponent claims X' implies X.

Answer 3

This is a textbook example of "faulty generalization" where a specific case is illegitimately taken as representative of a larger group. The most familiar form is "hasty generalization" where a larger conclusion is drawn from a very small dataset (as when a racist generalizes about an entire group of people from the one bad person of that race he or she has met).

This case is particularly egregious, since the conclusion actually contradicts the evidence, which is most naturally taken as implying that 20% of people prefer vanilla to strawberry.

There is an additional illegitimacy in the line of argument, in as much as preferring strawberry is not the same as disliking vanilla. This is perhaps a disguised version of the equivocal fallacy, where a term with one meaning in the given context is treated as if it had a different (related but distinguishable) meaning.

Answer 4

Prefer and like aren't the same thing.

It's quite plausible that everybody likes vanilla ice cream (after all, it doesn't taste of anything so no reason to dislike it) but they all prefer something else (which varies according to what actual taste they like).

It looks like ignoratio elenchi to me.