Is this a Fallacy? Not X because in past you argued Y. Does it have a name?

Suppose a year ago I defended one position based with an argument. Then today I argue the opposite position, based on an entirely new argument.

Now someone says that my current argument must be false because I argued for the opposite position one year ago. Note that the person isn’t refuting my argument’s premises, logic, or conclusions; rather, that person is stating that my having argued against it in the past implies that my argument for it today must be false.

Is this a fallacy? If so, does it have a name?

Here’s an example, similar to the circumstances that have raised the question:

Lawyers for The Developer argue that a land use law implied X in a court proceeding. A year later they argue that a land use law implies Not-X based on an entirely new line of reasoning. Ignoring whether the new argument successfully beats the old argument, the attorney for those opposing The Developer assert that The Developer’s argument for Not-X doesn’t pass muster because one year ago, The Developer’s lawyers argued in favor of X.

The attorney for the opposition does not address The Developer’s new argument in any way, shape, or form, but merely states that because The Developer went on record for X in the past, then his argument for Not-X today must be bunk.

Who was successful a year ago? Whichever side was ruled to be right then must be wrong now, and vice versa, unless the law has changed in the last year.

In other words, it’s not a matter of being a fallacy: it’s a matter that the law is what the courts say it is, and courts are bound (at least to some extent) by previous decisions. So if the developer argued X last year, and the court said then, “You’re wrong: not-X is the law here”, then the developer is perfectly correct to argue not-X this time.

It’s called “You Can’t Have It Both Ways.”

Or “Male Response To The Female Perogative”, though that one never, ever works.

I assume, africanus, that you admit your previous argument was in error, correct?

If you’re submitting that you were correct then, and you are also correct now, and if the situation is clearly on in which you’re arguing that both X and ~X are true, then you’re committing the fallacy of arguing an inconsistency, a type of non sequitur.

If, however, you’re arguing that you were wrong then, then I’d say the person with whom you’re debating is committing the fallacy of argumentum ad hominem: they’re arguing that something about you (mainly, your previous espousal of a different position) somehow renders the substance of your current argument false. That’s clearly an irrelevant argument: nothing about what you’ve said in the past has any bearing on the merits of your current argument.


Neither side was ruled to be correct on that particular point, nor was it a point of contention in court.

Worth noting is that I’m asking for a general principle and this case prompted the question, but the case is not the question. If I argue that passing a shall-issue cocealed-carry law in Texas would be bad and then, after seeing that my dire predictions fail to obtain, I change my stance, then someone could assert that my updated argument for my new position on gun control doesn’t float simply because in the past I had an argument for the opposite position.

“You oppose capital punishment?! Last year you were in favor of it, so you can’t be right now.”

Is that a fallacy? If so, what is it?


The closest thing I can think of is a Genetic Fallacy:

Your friend is saying that since the origin of the current argument comes from someone who previously argued the contrary, the current argument cannot be true. In the broadest sense it’s a fallacy of relevancy.

For some reason, I’ve been hearing the word “flip-flopping” around this year. :slight_smile:

Not really relevant to the question of fallacies, but here’s a good quote to use against people like that:

“A foolish consistency is the hobgoblin of little minds.” - Emerson. :wink:

The OP asks about logical fallacy, but posits an example arising out of law.

There is a legal principle which may be of use here" equitable estoppel. Equitable estoppel generally prevents a party from taking a different position at trial than they did at an earlier time if another party would be harmed by the changed position.

There are a host of caveats, but this is the general proposition.

Yes, that is correct. In the case of the precipitating situation, I feel that The Developer created an arugment for ~X that soundly crushes their previous argument for X (which was little more than an assertion). It is in that sense that I ask the question.

For example, the Texas gun law was a real incident. When I saw that my dire predictions were way off base and entirely wrong, I updated my view on gun control in light of the new evidence.

Another example would be the current Iraq war, where my (generally) pro-war stance converted to a (generally) anti-war stance on the basis of compelling arguments I encountered after having established my first opinion.

Thanks for the input, everybody. Good call on the question of law in terms of the precipitating event, since I am going to be involved with it, it was a helpful heads-up.

Left Hand of Dorkness is correct. Your opponent rejects your argument because of your previous conduct (asserting a contrary position to the one you now assert). He would be unable to reject the argument if it were advanced by someone else, who had not previously offered any argument. But the validity of the argument you know advance does not depend on who advances it. Rejecting the argument because it is advanced by you, rather than by somebody else, is the logical fallacy known as argumentum ad hominem.

Your opponent can legitimately criticise you for inconsistency, but that criticism tells us nothing about which, if either, of your arguments is valid.