Non Semper Ergo Numquam

Here’s a logical fallacy I’ve been coming across (and making) lately.

“Non semper, ergo numquam” means “Not always, therefore never”.

In response to pointing out some cause of an event, or a criticism of an idea, a person finds a counter example. That can’t be true because of a particular example when it is not true.

It is a kind of quantification fallacy, a false conversion, but from my research I could not find a name for it.

It is a fallacy because most of the time we make general statements not with the purpose of suggesting they apply in all cases, just that they are general enough to remark on. To undermine such a general statement it is not enough to respond with a counter-example.

So “natural selection drives evolution”… “here’s a situation where natural selection doesn’t drive evolution.”

Or “religion promotes supernatural nonsense”… “I’m religious and I don’t believe in the supernatural.”

Or “marijuana is not a particularly harmful drug”… “But my cousin did weed, and ended up in a psych hospital.”[1]

But still, the counter example is a tempting rebuttal, and a strong rhetorical trick. I’ve found myself often trying to justify the counter-example: trying to reject it or cast doubt on it. Which is a tacit acceptance that the generalization was supposed to apply in all cases. It inverts the discussion, so a reasonable statement gets turned into an unreasonable exclusive statement, and the person is forced to defend that unreasonable position. The correct response is more like “so?” But even that can feel like a weakening of the argument. Though I fight it, I instinctively love black-and-white certainties. And even when I am intending to suggest a matter is only a very dark shade of grey, it can be galling to be reminded it is not entirely black.

It is particularly galling when faced with someone with a tendency to commit the opposite fallacy: “aliquando ergo semper” (sometimes therefore always) – someone who will take the valid counter example as evidence that the matter is entirely white. Who’ll conclude that, if natural selection is not the mechanism behind all evolution then it can be entirely discounted, or that the presence of any historical material in the bible means the bible is historically accurate. In those cases an unambiguous counter claim would be preferable, for the same of rhetoric. But this fallacy is always there for the over-eager.

[1] Also an example of a post hoc ergo propter hoc fallacy.
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5 Comments

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5 responses to “Non Semper Ergo Numquam

  1. No comments here yet, but never too late, I hope:

    So, wait, you couldn’t find a name, so you named it? Is that what you were saying in your opening?

    I think there may be an ironic problem with your fallacy.

    You say:

    “most of the time we make general statements not with the purpose of suggesting they apply in all cases, just that they are general enough to remark on.”

    Here are the issues:

    See how you couched your statement with “most of the time”. When general statements aren’t couched, they are ambiguous and should be challenged. That is why we have words/phrases like “some”, “a few”, “most” etc.

    So, you point out “religion promotes supernatural nonsense” — should say, “religion often promotes supernatural nonsense”.

    It doesn’t matter what “the purpose” [read, "intent"] of the speaker is, they need to be careful of their words. Claiming your statement is OK as it stands because in your head you meant otherwise has to be a fallacy in its own right.

    Maybe there is not a word for your fallacy, because it is wrong for those reasons.

  2. Ian

    @Sabio, yup good points, there is a failure of communication when absolute language is used. But it is rare, I think, in normal dialog to ever mean absolute exclusivity. I struggle to think of anything I’ve said recently which was intended to be so exclusive that my argument would be destroyed by a counter example.

    Nazism is a vile ideology. I support equal rights under the law. Religion gives respectability to injustice. Smoking causes a range of health problems. I love warm bagels.

    I contest that any of these statements should ever be *presumed* to be universally quantified. We simply can’t spend the time qualifying everything we say with markers of probability and applicability.

  3. As language in an unspoken temporary morphing contract between two speakers, the use of unqualified generalizations is usually share for:
    (1) friends, fellow tribesmen/women, allies and such
    (2) those you wish to persuade who can’t see through the language
    (3) those you wish to brainwash
    (4) those you wish to piss off

    You are right, people won’t challenge unless the falseness of the generalization offends important points to them. Generalizations certainly speed up conversation which then may have to slow down when their convenient inaccuracy fails.

    Thus, I contend, no more need for the fallacy — it is not a falllacy.
    Just saying.

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