The question "What is the difference between 'impossible' and 'implausible'?" has generated an interesting discussion on the differences, if any, between "totally implausible" and "impossible".

More precisely, the debate arose from the following statement:

Probably, in some contexts, "totally implausible" could mean "impossible."

Since it seems that there is controversy on this matter, as the following comments show,

  • "there's certainly scope for disagreement about what exactly totally implausible means. There's no doubt in my mind that the negating im- prefix is doing something subtly different when applied to “plausible” vs. “possible”. Even if not everyone (or perhaps no-one) agrees with me on that point."

  • "implausible is often used thus, as if implausible and improbable were synonyms; and what is "totally improbable" is, by definition, impossible. But I think this is a misuse: "not seeming probable" is not the same thing as "not probable". Plausible speaks to perception, probable to fact."

  • "Not sure I agree that totally implausible could mean impossible. Why does the addition of the adverb change the meaning of implausible to impossible?"

I wonder: could "totally implausible" mean "impossible?"

  • possible duplicate of "Plausible" vs. "possible"
    – Robusto
    Dec 22, 2012 at 22:21
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    @Robusto: I think the specific issue of negation here makes this one a distinct question. You may take the view that plausible/implausible are interrelated in exactly the same way as possible/impossible, but that ain't necessarily so, and I think the complexities are even greater when coupled to an "absolute" modifier like totally. I don't say a single question/answer pair couldn't cover everything, but it certainly seems to me neither page currently achieves this. Dec 23, 2012 at 0:14
  • It could be used, but that would not be an accurate usage of plausible or possible. 'Totally implausible' = no one in their right mind would expect that to happen; 'impossible' = not possible at all (belief isn't part of it).
    – Mitch
    Dec 23, 2012 at 1:49
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    @Mitch: Except that from any plausible epistemological stance, impossible can only mean believed not to be possible. Dec 23, 2012 at 3:06
  • @FumbleFingers: lots of things are impossible well outside of belief such as logical or physical impossibilities.
    – Mitch
    Dec 23, 2012 at 3:44

2 Answers 2


I take Barrie's point that plausibility is primarily concerned with appearance rather than actuality. But I think there's a limit to how far one can take such strictly literal interpretations.

In most contexts, probable/possible mean likely/unlikely, but whereas the corresponding negated form improbable means not likely, impossible doesn't mean not unlikely - it means definitely not.

By the same token, convincing/plausible usually mean very believable/just about believable. I'm aware some people use plausible to mean convincing, but I think most people need something very/totally plausible to actually be convinced.

As John Lawler often reminds us, negatives [are] probably the most complex portion of English semantics and the weirdest part of its syntax.

And as Cerberus points out here, [probability] is a complicated issue [in the context of linguistics].

In my version of English, if something is implausible, it's unlikely, but at least feasible. But if it's totally implausible, it has no element of plausibility/feasibility whatsoever, and I personally do not distinguish that from impossible.

  • Erm, how does possible imply unlikely? From OED - Possible, that is capable of being; that may or can exist, be done, or happen. Impossible - not possible; that cannot be done or effected; that cannot exist or come into being; that cannot be. I beleive you're stretching the realms of plausibility! Dec 22, 2012 at 23:23
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    Erm, I mean in contexts where the speaker might use either or both word. For example, I think it's probable that I'm right, but I admit it's possible that you are. That leaves no doubt which of the two I consider most likely, and the opposite meaning would definitely apply if I were to reverse those two words. Stop being so literal-minded! Dec 22, 2012 at 23:30
  • Well, does totally possible change the meaning of possible? Does totally impossible change the meaning of impossible? Aka, does totally plausible change the meaning of plausible? Yet you're suggesting that totally implausible changes the meaning to not possible? It's not logical said Dr Spock. Dec 22, 2012 at 23:33
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    @spiceyokooko: This isn't going anywhere. You're determined to stick to strict literal/logical interpretations, and to ignore my points that (1) language isn't necessarily logical; (2) particularly not when it comes to negation; (3) even more particularly not when concepts involving probability and/or desirability are involved. I can easily cite you examples where totally implausible means impossible, and my point is not diminished by the possibility that you might feasibly find examples where it means possible, but not at all credible. Dec 22, 2012 at 23:47
  • And you're missing my point of why you would want to use totally implausible when impossible would be a better word that means the same thing? Why use two words when you can use one? Dec 23, 2012 at 0:02

Plausibility is concerned with appearance rather than truth. If something is implausible, whether totally so or not, then it doesn’t sound convincing, it doesn’t sound as if it’s possible. To say something is impossible, on the other hand, is to say that it really cannot be done, not just that it seems that it cannot be done.

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    @spiceyokooko: Of course adverbs can radically change meanings. Would you rather be dead, totally dead, or just somewhat dead?. In most contexts, your chances of surviving either of the first two are non-existent, so arguably totally there is meaningless. But with somewhat, it's practically a dead cert that you're still alive. Dec 22, 2012 at 22:13
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    I don't think this invalidates the quotation. To extend Fumblefingers' example, "In some contexts cut in half could mean (or at least include) 'dead'", though dead certainly does not mean cut in half. Dec 22, 2012 at 22:41
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    @spiceyokooko: Well, we know you think in this instance it doesn't change meaning, since you've effectively said several times that you don't believe implausibility can be so extreme as to deny possibility. But I see no reason to suppose implausible is unusual in the sense of not being capable of adverbial modification. And per my own answer, I see two very good reasons for supposing that idiomatically, it's a far more "malleable" word than most. Dec 22, 2012 at 23:39
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    If everyone took your position, languages would never change to any significant degree (you'd just get the occasional new word, when we invented something that didn't previously exist). In practice, SE (and the study of language in general) is more about actual use of language, not correct use as defined by those people who decry its "misuse". Dec 23, 2012 at 0:04
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    @FumbleFingers The question is Where do you draw the line? --because there must be a line or language is (literally) impossible. For instance: I intensely dislike the contemporary trend toward redefining reticent as reluctant, not least because it takes a fine chisel out of my toolbox and turns it into a second-rate screwdriver. Am I to follow the trend, or resist it? Dec 23, 2012 at 1:34

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