Actually we can answer that question with a bit more precision than you might think because we can track the production of manuscripts down through the centuries - obviously that doesn't really give us a figure since we don't know how many readers each manuscript would have had, plus a lot of manuscripts would be lost. In this particular case, the Periphyseon is absolutely massive, so not easy to copy, and there are I believe only a small handful of manuscripts which incidentally show revisions, probably at the behest of Eriugena himself. We know of several readers in the immediate generations following him - episode 102 will actually touch on this. So, not a huge distribution. By contrast a work like, say, Isidore's Etymologies would have been in every good library in Europe and had thousands of readers in the 8th-9th centuries alone, I'm guessing. But you need a real manuscript expert to give you better answers; maybe one will add a comment here if we're lucky!
Audience
Actually we can answer that question with a bit more precision than you might think because we can track the production of manuscripts down through the centuries - obviously that doesn't really give us a figure since we don't know how many readers each manuscript would have had, plus a lot of manuscripts would be lost. In this particular case, the Periphyseon is absolutely massive, so not easy to copy, and there are I believe only a small handful of manuscripts which incidentally show revisions, probably at the behest of Eriugena himself. We know of several readers in the immediate generations following him - episode 102 will actually touch on this. So, not a huge distribution. By contrast a work like, say, Isidore's Etymologies would have been in every good library in Europe and had thousands of readers in the 8th-9th centuries alone, I'm guessing. But you need a real manuscript expert to give you better answers; maybe one will add a comment here if we're lucky!