Converse Error: Difference between revisions
Content added Content deleted
Looney Toons (talk | contribs) (Removed reference to the Ad server) |
Looney Toons (talk | contribs) (Reordered sections, fixed a "current" reference) |
||
Line 27:
:: Note that, by the [http://en.wikipedia.org/wiki/Contrapositive contrapositive] rule, these two fallacies are equivalent. For example, you could replace "If a person is wearing a hat, they have a head" by the logically identical statement "If a person has no head, they aren't wearing a hat" to turn the first example of denying the antecedent into an example of affirming the consequent.
{{examples|Examples:}}▼
* In ''[[American Dad (Animation)|American Dad]]'', Stan sinks his entire savings to build a rocket for Steve to win a contest.▼
{{quote| Stan: You gotta spend money to make money.<br />▼
Francine: But you didn't make any money!<br />▼
Stan: So logically, I didn't spend any money! [[No Fourth Wall|*waves at the camera*]] Goodnight everybody! }}▼
* A current argument made by Obama supporters against conservatives.▼
{{quote| Racists who don't like black people oppose Obama's presidency<br />▼
Bob opposes Obama's presidency<br />▼
Therefore Bob is a racist. }}▼
** This is not to say that you can't make an argument that someone that opposes Obama is a racist, but it does not follow automatically from being opposed to his presidency and/or policies. ▼
** A similar argument from Obama detractors is that anyone who voted for Obama did so only for affirmative action's sake, rather than because they believed Obama was a strong candidate on his own merit.▼
** I opposed Obama because I was for Hillary, [[Hypocritical Humor|you sexist!]]▼
▲==== Looks like this fallacy but is not: ====
* Inference to the best explanation. The usual form of scientific reasoning, as well as a lot of Sherlock Holmes' "deductions" (though he's wrong to call them that, since this is a form of ''inductive'' reasoning).
{{quote| B.<br />
The best explanation for B would be A.<br />
Therefore, A (probably). }}
** This differs from the Ferrari example above in that it posits a stronger connection between A and B than just A's truth entailing B's; B is actually giving some positive reason to ''prefer'' A over the other possibilities. (This approaches, without actually becoming, the logical relationship "if and only if".) Also, this form of argument isn't claiming deductive certainty, so the bar is a little lower for it being acceptable.
** Scientific reasoning is frequently attacked by those who understand this fallacy, but not the scientific method, which has the following form:
{{quote| B.<br />
Line 56 ⟶ 43:
Not D!<br />
I must provisionally reject A or modify it to account for D, then continue to seek new information and propose new possible explanations. }}
▲{{examples|Examples:}}
▲* In ''[[American Dad (Animation)|American Dad]]'', Stan sinks his entire savings to build a rocket for Steve to win a contest.
▲{{quote| Stan: You gotta spend money to make money.<br />
▲Francine: But you didn't make any money!<br />
▲Stan: So logically, I didn't spend any money! [[No Fourth Wall|*waves at the camera*]] Goodnight everybody! }}
▲{{quote| Racists who don't like black people oppose Obama's presidency<br />
▲Bob opposes Obama's presidency<br />
▲Therefore Bob is a racist. }}
▲** This is not to say that you can't make an argument that someone that opposes Obama is a racist, but it does not follow automatically from being opposed to his presidency and/or policies.
▲** A similar argument from Obama detractors is that anyone who voted for Obama did so only for affirmative action's sake, rather than because they believed Obama was a strong candidate on his own merit.
▲** I opposed Obama because I was for Hillary, [[Hypocritical Humor|you sexist!]]
{{reflist}}
|
Revision as of 19:19, 18 December 2013
Has nothing to do with shoes.
Affirming the consequent:
- This claim is most simply put as:
If A, then B. |
- It's a fallacy because at no point is it shown that A is the only possible cause of B; therefore, even if B is true, A can still be false. For example:
If my car was Ferrari, it would be able to travel at over a hundred miles per hour. |
- This is popular in conspiracy theories. Here the fallacy is fairly obvious; given the evidence, the car might be a Ferrari, but it might also be a Bugatti, Lamborghini, or any other model of performance car, since the ability to travel that fast is not unique to Ferraris. Hell, it might even be a Subaru Outback. Note that while this may appear to call all hypothesis / evidence experiments fallacious, they are based on additional evaluations of the likelihood of other theories, thus establishing that A is a likely cause of B.
Denying the antecedent:
- The flip side of the above, where you say that because the initial conditions did not happen, the result is impossible.
If a person is wearing a hat, they have a head. |
- Note that, by the contrapositive rule, these two fallacies are equivalent. For example, you could replace "If a person is wearing a hat, they have a head" by the logically identical statement "If a person has no head, they aren't wearing a hat" to turn the first example of denying the antecedent into an example of affirming the consequent.
Looks like this fallacy but is not:
- Inference to the best explanation. The usual form of scientific reasoning, as well as a lot of Sherlock Holmes' "deductions" (though he's wrong to call them that, since this is a form of inductive reasoning).
B. |
- This differs from the Ferrari example above in that it posits a stronger connection between A and B than just A's truth entailing B's; B is actually giving some positive reason to prefer A over the other possibilities. (This approaches, without actually becoming, the logical relationship "if and only if".) Also, this form of argument isn't claiming deductive certainty, so the bar is a little lower for it being acceptable.
- Scientific reasoning is frequently attacked by those who understand this fallacy, but not the scientific method, which has the following form:
Examples:
- In American Dad, Stan sinks his entire savings to build a rocket for Steve to win a contest.
Stan: You gotta spend money to make money. |
- An argument made by Obama supporters against conservatives.
Racists who don't like black people oppose Obama's presidency |
- This is not to say that you can't make an argument that someone that opposes Obama is a racist, but it does not follow automatically from being opposed to his presidency and/or policies.
- A similar argument from Obama detractors is that anyone who voted for Obama did so only for affirmative action's sake, rather than because they believed Obama was a strong candidate on his own merit.
- I opposed Obama because I was for Hillary, you sexist!