there are/were two persons understanding Confucius.
 

There is a professor who understands Confucius.
He is alive.

There was another man three hundred years ago who undestood Confucius. He is dead.

so:

there are/were two persons understanding Confucius.

which verb should be used?
( the sentence structure 'he is ..., so was...' I find it impossible to use)

Re: there are/were two persons understanding Confucius.
 

Here you could rephrase it as : There have only ever been two people with a good understanding of Confucius' philosophy : XXX, who lived in the Xth century and XXXX, who teaches at the university of XXX. Or whatever the details are. It's the same problem as before - the lack of a single verb for both people. So I've replaced ..who understood/understand with the noun phrase : with a good understanding of

Re: there are/were two persons understanding Confucius.
 

thank you vey much.

I always use AT university, as you did, and the Oxford collocation dictionary only includes AT as a preposition preceding UNIVERSITY, but dictionaries may not be comprehensive enough, and sometimes I see IN university; is it acceptable?( I only know IN and AT are acceptable for SCHOOL, with a difference in American and British Usage

Re: there are/were two persons understanding Confucius.
 

I fed them into a concordancer (CORPUS CONCORDANCE ENGLISH) and got ten examples of "at university" as opposed to none of "in university". However, I got 17 examples of "in college" as opposed to 10 of "at college". Broken down by variety, the results were :

at university - all British English
in college - all but one Am. Eng.
at college - mixed, but twice as many Brit Eng than Am Eng.

I was expecting to find "in school" in Am Eng referring to both grade school and university, but in fact all the examples that came up were for grade school.

Re: there are/were two persons understanding Confucius.
 

could you tell me what a concordancer is?

I do not know how to use it and the result yields nothing

Re: there are/were two persons understanding Confucius.
 

A concordancer is a software programme which analyses a corpus of material to see how frquent words and phrases are, what collocations occur etc. To use the lexTutor concordancer to find the results that I mentioned :

a) click on the link.
b) at university (or whatever word/phrase you want to analyse) into the box
c) move to "Choose a corpus". if you want to check Am.Eng click on Brown; If you want written Brit.Eng, click on BNC written; if you want spoken Brit.Eng, click on BNC spoken. Or you can click on All of the above if you don't need to distinguish the variety - try that first. (The other corpora on the list give you the possibility to check specialist uses like Medical or Legal English).
d) Click on Get concordance. You'll see a list of all the uses of "at university" in the corpora you have chosen.

There are other boxes but ignore them for now - they give you more advanced options.

Re: there are/were two persons understanding Confucius.
 

thank you very much