Could possibility or hypothetical

Question

Please let me know if could in the following sentences shows a hypothetical situation or possibility.

1. He couldn’t lift that. It’s too heavy.
2. He could lift that. It is not too heavy.

Answer 1

1 He couldn’t lift that. It’s too heavy.

This could mean:

1A He tried to lift that, but was not able to because it was too heavy.

or it could mean:

1B It would not be possible for him to lift that. It weighs more then he is able to lift.

In short, 1 could be either the description of a past event 1A or the hypothetical 1B. Without context there is no way to tell, but perhaps meaning 1B is a bit more common.

Sentence 2 is a similar case.

2 He could lift that. It is not too heavy.

This could mean:

2A He tried to lift that and was able to do so. It was not too heavy for him to lift.

or it could mean:

2B He would be able to lift that if he tried. It is not too heavy for him to lift.

Again, whether 2A or 2B is meant requires context.

This means that sentences 1 and 2 are symmetrical. Either could be describing the result of an actual past event, or be predicting the outcome of a hypothetical future event, and in neither case can one determine which is meant without additional context. Tjhe words "could" and "couldn't" can be used in both of these senses, and fluent speakers do so normally.

Answer 2

1 ) He couldn’t lift that. It’s too heavy.

I'd say this version can only refer to (negated, denied) capability / possibility (he doesn't have the ability to lift it). If a thing isn't possible, it can hardly be proposed as a hypothetical scenario. But for the non-negated version...

2 ) He could lift that. It is not too heavy.

...it depends entirely on context whether the speaker is...

2a ...asserting that he has the ability to lift it
OR
2b ...referring to a possible - but not (yet) actual - hypothetical situation / course of action.

For example, interpretation 2a would apply if the speaker was discussing whether or not his friend should apply for work with a delivery company, it having just been pointed out that their workers are expected to lift parcels weighing up to 50Kg - hence it's a reference to "ability".

But interpretation 2b would apply if, say, a woman was trapped under a fallen tree, and our speaker was suggesting that the best thing to do would be for her husband to lift the tree up so they could pull her out - hence it's a reference to "possible scenario".

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Context usually makes it obvious which sense of can / could is intended. But consider this interaction after a Sunday roast dinner...

(Wife) "You could help with the washing up!"
(Husband) "I could, but I think I'll watch the football match on TV instead."

(probably with heavy stress on highlighted term in both cases). Here, the wife uses could to refer to a (desirable, from her point of view) hypothetical scenario. The husband obviously understands this perfectly well, but his (irritating, perhaps) reply pretends that he's responding to the you have the ability interpretation.