Invoking “divine inspiration” is simply a semantic sleight-of-hand.
Unsupported assertion. And also a false assertion. As a matter of fact, you actually effectively admit that there is a difference between divine inspiration and divine authorship when you say:
When you separate inspiration from authorship, you acknowledge that human minds, languages, cultural assumptions and rhetorical conventions did the real work.
As has been discussed, even Paul emphasizes understanding as being of prime importance, and Paul never denies that understanding is always dependent on human effort.
There is no empirically verifiable difference between a human poet struck by “inspiration” and a self-described prophet claiming the same.
So, now that you have indubitable reason to retract your non-sense about "a semantic sleight-of-hand", you might be able to realize that human understanding is not limited to what is "empirically verifiable" and that human understanding is not necessarily claimed to be necessarily superior for seeming to have been divinely inspired.
Modern psychological research shows that “inspiration” is indistinguishable from ordinary creativity and memory reconstruction.
You need "[m]odern psychological research" in order to be aware that understanding relates to one's own creativity? Sheesh. What a sad, very sad, maximally sad reference to "research". Your remark would have been much better if it had been based on your own experience.
The divine inspiration at issue does not eliminate - nor even diminish - the need for the personal creativity which gives rise to understanding. Indeed, it would be very much the opposite: an experience of such inspiration stimulates realization of the need for a more developed understanding.
If God really inspired Paul’s words, why did later copyists feel free to alter them—adding clarifications, smoothing grammar, even inserting entirely new sentences?
First of all, precisely because they are not God's words. But even if they were God's words, and as was discussed earlier, even God's words could be altered since even God's words would have been limited by the limits inherent to human language with such limitation itself always providing and allowing for expression modification.
Besides all that, Paul's words are not to be idolized. No words are to be idolized, because understandings are always to be further developed. It is quite possible that some copyists imagined themselves as communicating and furthering an already furthered understanding.
Also keep in mind the related matter of translation. All translation is or becomes interpretation. Of course, even without translation from one language to another, all understanding that communicates is interpreted in order to become understood. All understanding is subjective, personal, and that is the case with or without reasoning that is based on intersubjective agreement regarding empirical matters.
When talking about God, the issue is always human understanding.
There is zero evidence of anything beyond human politics and psychology at work. Attaching “divine inspiration” afterward is just a post hoc stamp of approval with no independent warrant.
Yet another incorrect attribution. Within this discussion, noting the difference between divine inspiration and divine authorship is utterly disconnected from matters having to do with approval. Rather, noting the difference between divine inspiration and divine authorship is entirely intended to set focus upon matters regarding the nature or process of human understanding.
Focus is set upon human understanding if and when love of neighbor, love for an other person, is held to be important. Love for the other person is inseparable from undertaking to understand the understanding had by that person, and understanding that understanding is necessarily dependent on the ability to consider context as part of perspective. The pseudo-argument against Paul at issue in this thread evidences next to no concern with context.
Although the pseudo-arguments against the possibility of divine inspiration evidence not the slightest interest in love for neighbor, that love can be atheological. Indeed, even when a religious person creates acts of love, they are atheological not only because they are not being done by God but also because they are intended entirely for the sake of the other person. And maybe that fact will provide for some insight into a perspective regarding God which is applicable with or without belief in the actuality of God, because it really has to do with the nature of a love for an other. And maybe that fact will provide some impetus for realizing that trans-perspectival viewpoints are, more often than not, superior to merely "empirically verifiable" perspectives.
There is nothing substantive to “deal with,” because divine inspiration is defined in such a way that it cannot be tested or disproven. You say inspiration isn’t authorship—but you still rely entirely on human evidence to defend it
Inspiration is a matter of experience; it is not a matter of evidence. Inspiration is always an experience which changes perspective or at least affects understanding. It is not the experience which ultimately matters; it is the understanding affected by the experience and effected after the experience which ultimately matters.
There is simply no non-circular way to rescue “divine inspiration” from being an article of faith rather than an established fact.
If you think that there has been an attempt "to rescue 'divine inspiration'", then you have badly misunderstood. The only fact of the matter is that the argument at issue and as presented fails as a logical argument against Paul's claim that "the gospel I preached is not of human origin" because that failed argument relies on (and never gets beyond) the notion that Paul claims that the gospel he preached was divinely authored. A fatal flaw with that argument persists. Consider the following:
''Divine inspiration'' implies that God is the author.
You see, that is an example of an actual attempt to rescue - in this case, it is an attempt to rescue divine authorship, with that attempt at rescue serving as an attempt to rescue the argument (such as it is) presented against Paul. The rescue fails, because the term "implies" is an acknowledgement that divine inspiration is not necessarily divine authorship and, therefore, that divine inspiration allows for human influence and creativity.
human influence waters down the authority of the message.
The whole pseudo-argument has a limited understanding about
authority. That limited understanding is common and has nothing to do with belief or lack of belief in God. The sort of authority not taken into acount by the pseudo-argument and its defenders relates to inspiration and understanding. It is authority without imposition. The substance of understanding follows after an experience of authority, but it is not authority or the experience of authority which produces the substance of the understanding which follows after an experience of authority. Human influence does not dilute authority even if human influence affects understanding.