I"ve been trying to figure out the tones for the character 论. It seems like it is fourth tone in 讨论. However, in something like 一概而论 I'm not entirely sure. Is this a taiwan/Mainland division? Or is it decided on a word by word basis?
Old Pekin dialect (>50 years ago) pronounce it as lin(4th tone) and that might be influencing some other dialects.
I am not sure about the situation in TW, but mandarin standard is lun(4th tone) except for 论语, habitually lun (2nd tone).
论 ，there are two tones. second tone and fourth.
Mostly，论 is fourth tone.It is a verb.
Only in the situation of 论语 ，论 is the second tone.
论语 is an old book writtern by Confucius‘s students,recording what Confucius said!
It should be the 4th tone.
Actually, every "论" has the same meaning is the 4th tone, such as “讨论”(discuss) “理论”(theory).
“论” in the word “论语” is specially the 2nd tone because it doesn't means like that.
When the 论 is the 2nd tone, it should be in classical Chinese and means:
说得尽(some thing you want to say can be finished)(is always used when there is so much thing you want to say but you can hardly finish them.)
表达，抒发(Express something you want to.)