Meaning?

Hi. Does this passage imply that the developed emotional attitudes of a writer fall under four motives? Thank you in advance.

I give all this background information because I do not think one can assess a writer's motives without knowing something of his early development. His subject matter will be determined by the age he lives in — at least this is true in tumultuous, revolutionary ages like our own — but before he ever begins to write he will have acquired an emotional attitude from which he will never completely escape. It is his job, no doubt, to discipline his temperament and avoid getting stuck at some immature stage, in some perverse mood; but if he escapes from his early influences altogether, he will have killed his impulse to write. Putting aside the need to earn a living, I think there are four great motives for writing, at any rate for writing prose. They exist in different degrees in every writer, and in any one writer the proportions will vary from time to time, according to the atmosphere in which he is living. (Why I Write-George Orwell)