SOURCE   Attack on Titan, 2013 Anime Season 2, Ep. 7

What is the difference between "Since when could he move so quick?" and "Since when can he move so quick?"

The original sentence is the version with could, but I'm wondering if it has the same meaning with can.


The question refers to a moment in time which lies in the past, in relation to the moment that the question was asked:

At which moment did he start being able to move so quickly?

would be equivalent in meaning to the orignal question.

At which moment in time does he start being able to...

clearly doesn't make sense when referring to a moment in the past. That's the reason why could is semantically more correct then can, even though it's not as obvious when using this form.

On a sidenote: the adjective quick should be replaced by the adverb quickly.

Also note the comment by @p-e-dant, which mentions the use of the modal verb could to highlight a present ability/possibility. This is another possible interpretation, although I find it doesn't completely apply.


The problem is that both of these sentences are very linguistically incorrect. A more correct expression would be something like:

“Since when has he been able to move so quickly?”

In many cases, the answers to questions like yours are more obvious when the sentence is spoken or written correctly to begin with.

  • Given that the sentence was taken from an apparent battle scene in an action anime series, though, we don't expect the characters to speak in "linguistically correct" language. We expect them to talk like warriors on a battlefield. And your answer should also try to answer the question; namely, does the meaning of the original change if we use can instead of could? – J.R. Aug 14 at 9:32

Could is an obsolete past tense of the word can. The words are roughly equivalent auxiliary verbs. There is a shade of meaning in the word could that expresses doubt.

It could be true. as opposed to It can be true.

There is a difference between Can I play poker? and Could I play poker?

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

  • 1
    Really, B.W.? Where on Earth did you get the idea "Could is an obsolete past tense of the word can", please? – Robbie Goodwin Jun 4 '18 at 23:52

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