If I were to say something like:

  • "They couldn't have done X."
  • "They're incapable of having done X."
  • "It's not possible that they did X."

It can be interpreted in one of two ways:

  1. They're morally/psychologically incapable of doing X (like I'm physically capable of murdering someone, but I'd never be able to bring myself to do so).
  2. It's physically/logistically/biologically impossible for them to have done X (like it's impossible for the government to fake the existence of the Moon).

Is there any single word which will convey meaning #2, so I won't have to use some wordy phrasing like "they couldn't do it even if they wanted to"?

  • 4
    Strictly-speaking, impossible covers #2 while unthinkable covers #1. Unfortunately, impossible has now expanded to cover #1 as well. – Lawrence Aug 1 '17 at 7:39
  • I'd call it a "sentence". Your #2 definition does not properly describe the sentence as it does not capture the "unwilling" aspect. – Hot Licks Aug 1 '17 at 11:56
  • I think you'd get closest by using wouldn't instead of couldn't. – Robbie Goodwin Aug 15 '17 at 15:14

Physically impaired

  1. Weakened or damaged.

Psychologically incapacitated

  1. Prevent from functioning in a normal way.

Impaired and incapacitated can generally be used interchangeably too.

Logistically impractical

  1. North American: Impossible to do; impracticable.

Also, [not] feasible

Possible and practical to do easily or conveniently.

Morally bound {to do [or not do] something}


1.1. Obliged by law, circumstances, or duty to do something.

Source used: Oxford English Dictionary

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