His language changes through the various letters he wrote. And Paul's Greek changes the way other writers after him use the language. Tracking the influences on Paul and Paul's on others could be a dissertation, or a lifetime of study. I think Paul was as much influenced by Aristotle and his Greek as anybody. Paul clearly was engaged in (if he didn't explicitly recognize) the sort of gripes that Socrates, Plato, and Aristotle had with the language and language flux of the old poets and playwrights and sophists (such as Homer, Hesiod, Sappho, Heraclitus, Sophocles, Euripides, Protagoras, Epicurus, Zeno, Gorgias, Dissoi Logoi). When Paul was in Athens listening in on and then chiming in on the conversations of his contemporaries in that City and culture, he used the Greek language rhetorically in a very Aristotelian way, starting syllogistically with the givens of certain men of old. He treats theo-logy in his speech in many ways as Aristotle does, an acknowledging of truths but of errors to get at the Nature of God objectively.
Paul, unlike Aristotle, did acknowledge much of his personal change, his "growth" perhaps, and certainly his dramatic adult human conversion. In his short life, the rippling effects of that conversion can be seen in his letter writing. Bill Heroman does some wonderful reflecting on and some reconstructing of the possibilities of some of this change in Paul. T.C. Robinson challenges whether there's a theological construct in the traditional ordering of Paul's New Testament letters. Bill Mounce has looked at Paul's rare Greek such as δί·λογος / dí-logos /. And Joel Hoffman, with a number of others, has wondered whether Paul has new meanings for σάρξ / sarks /.
Language, Greek language, and translation scholar Willis Barnstone reflects on Paul. Barnstone sees the stability of the Greek language, its fluidity, and where Paul fits into that. On pages 114 and 115 of his new Restored New Testament, Barnstone gets us thinking:
The letters to the Romans (probably his last letter) and the Corinthians show Paul at the peak of thought and rhetorical magic. He achieves language magic in demotic Greek (Koine), with a flare of the classical period while keeping to the simplified syntax and virtues of the vernacular. He has the high flow of Plato, who wrote in Attic Greek, in his own less inflected tongue. To repeat my argument [i.e., Barnstone's argument] about the glory of Mark's Greek, Paul's work is not less effective for being composed in vernacular development of Attic Greek any more than Michel de Montaigne is less for writing in French, the regional vernacular of Cicero's Latin. Indeed, in terms of change, Paul's Greek is closer to Plato than E. M. Forster's English is to Shakespeare. Greek, in spelling, grammar, and usage, was very early established, while in English the dictionary thoroughness of Samuel Johnson, who established norms for English spelling and usage did not enter the scene until midway between Forster and Shakespeare.
If this volume [i.e., Barnstone's Restored New Testament] were predominantly a study Bible, then it would begin with Paul’s I Thessalonians, which, if not supreme, carries the authority and beauty of all his authentic letters. And despite the above encomia [i.e. Barnstone's own praise] for the apostle’s key letters, there are advantages at least for study purposes to keep in mind the probable order of Paul’s work. He grows as his movement grows, and his work moves to the climactic pivotal letters. A chronological order, even the thought of one, would provide an unbiased historical frame for secular and sectarian events and reveal the material culture scene of the Jews, Christian Jews, Greeks, and Romans who participate in the drama of each book.
While I separate the authentic Pauline letters from the pseudonymous, from a stylistic point of view, the would-be Paul letters do not jar. Being pseudepigraphic they imitate Paul's style, in not his depth and breadth.While Barnstone may be making a few sweeping statements, he's absolutely correct to try to see Paul's writings and his Greek in light of developments in and of the language. Barnstone goes on to instruct his own readers in what Aristotle taught as if to help us read Paul better. That point shouldn't get lost on any of us. Why would it hurt any of us to get at not only exactly what Paul meant by certain Greek words but also at exactly how and why (sometimes without self reflection at all) we read Paul?