To express the idea of:
How come you're so[that much / this much / to this extent] sure of it?
The following phrasings all seem to be saying more or less the same thing:
Почему ты в нем столь / настолько / так уверен?
But I wonder if and how they are nuanced? Also, if I use any of these words with
твёрдо (like in `столь/настолько/так твёрдо уверен) - will it make a difference?