Usage of 非不 in Middle (?) Chinese I encountered this line: 色生，生故計是我，非不生。and as an amateur, I was confused by the two negatives in a row (非不), which was followed by 生, and when I tried to figure out what it might mean, I figured it might be a rhetorical way of saying "no [this, referring to what was just talked about,] without 生".

Someone more learned than I corrected me and said 非不生 was, instead, "not without 生". Forgive me if I ask too basic a question, but is this a common usage for 非不?
色生，生故計是我，非不生。


This statement comes for a Buddhist Sutra, Saṃyukta Āgama (雜阿含經). It is not easy to understand if one has no training in Buddhism.

As these words contains lots of logic in Buddhism translated from Pāḷi language, it is pretty obscure to most people. But it is required to distinguish everything in the logic of Buddhism.

You can view 非不生 this way. These is 不生 and one negates it to 非不生. It is like English, "impossible" and "not impossible". 

Those double negatives are quite common in Buddhist writing. If you know 心經, there is a phrase 無無明，亦無無明盡，乃至無老死，亦無老死盡。無無明 is the negation of 無明.