Like a piece of paper that could express a finely balanced argument? (3-5)
I believe the answer is:
two-sided
I believe this clue is a double definition.
'like a piece of paper' is the first definition.
(a piece of paper has two sides)
'that could express a finely balanced argument?' is the second definition.
(with two sides of an argument)
(Other definitions for two-sided that I've seen before include "Having a pair of aspects" , "Double-faced" , "covering both opinions" .)