Currier A and B

[Emma May Smith]

Both the script and the language could be the same, but the orthography may be different, which is indeed very likely if the script or the language were not commonly written. Here are lines from a Middle English poem, in two different manuscripts:

But here we do have a single manuscript, not two different ones. Why would the orthography evolve? And, further, is it evolution or a stepwise change?

I don't know why the orthography would evolve. I'm seeking a model/process that fits the observation that the text changes over the course of the manuscript. Though the simplest reason for it would be that the script or language are new to being written, and the writer address problems as he finds them.

As to the nature of the changes, I'm not sure what the difference between evolution and stepwise would be here. Any orthography would be a set of discrete rules within the writer's head. Each one is either true or false at any given point in the manuscript. Multiple rules may have been changed at once, and some rules may have had a bigger effect than others.