He had learnt a lot since he had been here.

[kadioguy]

[My sentences]

a. He has learnt a lot since he has been here.
b. He has learnt a lot since he was here (=He has learnt a lot since he left here).

(a) and (b) have opposite meanings. However, if we do backshifts of them, then:

c. He had learnt a lot since he had been here.
d. He had learnt a lot since he had been here.

They look the same. So how could we know what they really mean? I mean, (c) and (d) could mean either (a) or (b). And (a) and (b) are opposite .

(Edit: Fixed a typo)

 

[kadioguy]

So, context will tell us, for example:

1. Tom had studied abroad for several years. His parents believed that he had learnt a lot since he had been here (=b, if in the present tense ). They hoped to see him back home soon.

2. It was time for Tom to go. He had learnt a lot since he had been here (=a, if in the present tense). Now he was going to back home.

(Edit: Improved the content)

Is this right?

 

[kadioguy]

(Following post #2)

A friend told me, "It seems more natural to keep the distinction by substituting 'while' for 'since' in (2): He had learned/learnt a lot while he had been here."

Me: Do you agree that context will tell us?

Friend: With enough of it, yeah.

Me: Basically, do you agree with what I said in the original question?

Friend: With the caveat that you can make a version that's easier to read and solves the issue, yes.
----
I agree with them. However, I'd also like to hear your opinions.

 

[Tdol]

I see no reason for using the past perfect in #1.

 

[kadioguy]

I see no reason for using the past perfect in #1.

I was writing a story told in the past tense.