The Present Perfect for general statements

[abaka]

The use of present tense can in this sentence effectively places the possibility in the present, providing a somewhat more general, and 'theoretical' possibility than could. Very generally speaking, we tend to talk about facts and theories about the world in the present tense.

This is the one area where I disagree -- possibly because Canadian English differs from British English.
"Could" to me is distinctly more theoretical than "can".

Just as "might" is a humbler and more remote form of "may" (compare "May I have a bit of earth" and "Might I have a bit of earth?" -- Frances Hodgson Burnett), "could" is a more remote, hypothetical, conditional form of "can".

I must repeat that I strongly suspect regional differences are at play here.

 

[GoesStation]

Thank you for your corrections. I understand that syntactically this sentence is not interrogative, it just sounds like indirect request.



For example, "You can't have done it" might mean "I'm so shocked that refuse to believe you did it". GoesStation mentioned above that I confused this construction with the causative can, but I don't quite understand what it means. Does he mean that "can have done something" and "can + have something done" (like in "I have my car washed every Sunday" -> "I can have my car washed every Sunday") are different constructions?

If so, then "I want to know if there is anything else I can have done now to make myself look pretty" might mean "I had X done, and I had Y done. But I'm still not happy. Now I can have anything else done, but I have no idea what it might be."

Sorry, I meant the causative have.

 

[jutfrank]

The sentence doesn't use can have done in the way this thread is discussing. It's using the causative can to talk about various things you can direct somebody to do in order to make you more attractive.

Ah, yes! I see it now. Well-spotted. It's using the structure: have something done.

I somehow missed this crucial post before, sorry.

 

[jutfrank]

This is the one area where I disagree -- possibly because Canadian English differs from British English.
"Could" to me is distinctly more theoretical than "can".

Just as "might" is a humbler and more remote form of "may" (compare "May I have a bit of earth" and "Might I have a bit of earth?" -- Frances Hodgson Burnett), "could" is a more remote, hypothetical, conditional form of "can".

I must repeat that I strongly suspect regional differences are at play here.

I obviously didn't make it clear enough what I meant by 'theoretical' and I see how the use of that word may be considered problematic. I didn't mean hypothetical.

Let me put things in different terms ('general' versus 'specific' possibility), with examples:

According to Einstein's general theory of relativity, nothing can travel faster than the speed of light.

This is what I mean by the theoretical use of can. The statement expresses a theoretical limit to possibility. The use of can makes a general statement of what is possible. That is, we use it to say that things are generally true or false, according to some theory that we hold.

Temperatures in Siberia can drop to a staggering -70 degrees Celsius.

This is another example of what I mean by general possibility.

By contrast, when we use could, we often tend to be talking about the possibility of the occurrence of a specific event.

If there are regional differences, by the way, I would very much like to discover exactly what they are.

Moderators—I would understand if you think this thread has distracted from the original question but I do think that there are essentially two separate questions here—one to do with have done versus do and the other to do with can versus could.

 

[abaka]

If there are regional differences, by the way, I would very much like to discover exactly what they are.

After your clarification, I gather there aren't many in this case after all.