These categories pound came up with...
1.Inventors. Men who found a new process, or whose extant work gives us the first known example of a process.
2.The masters. Men who combined a number of such processes, and who used them as well as or better than the inventors.
3.The diluters. Men who came after the first two kinds of writer, and couldn’t do the job quite as well.
4.Good writers without salient qualities. Men who are fortunate enough to be born when the literature of a given country is in good working order, or when some particular branch of writing is ‘healthy’.
5.Writers of belles-lettres. That is, men who didn’t really invent anything, but who specialized in some particular part of writing, who couldn’t be considered as ‘great men’ or as authors who were trying to give a complete presentation of life, or of their epoch.
6.The starters of crazes.