Sorry, I seem to have been neglecting not merely the thread but the whole site! At the moment I'm busy scrabbling to prepare for "blended" online/masked classes, which mainly seems to involve writing subtitles for my own video lectures.
On Plantinga, I am not an expert on this argument but it's always seemed to me that it rests upon the supposition that a belief can be "warranted" only if it is formed by a process that was deliberately designed to produce true beliefs. And this supposition seems to me to be pretty dubious and basically one that begs the question. It's possible that I misunderstand Plantinga here.
(Although, if I may be smug for a moment, I did recently publish a paper in which I demolish Plantinga's argument about something completely different, so maybe I'm onto something on this one too!)
That is a strange claim, since there is so little evidence of the concept prior to the rise of the (Biblical) ideas of sin and punishment. A few commentators like Aristotle bring it up but they seem to consider it a minor issue in the theory of mind rather than something important.
This is correct, though doesn't go far enough. "Free will" as a concept didn't really arise until late antiquity, in the context of theological debates. Aristotle had no concept of "free will". He discussed under what conditions actions should be considered
hekousion ("voluntary" or perhaps "intentional"), which isn't really the same thing. It's not a biblical concept either.
Indeed "free will" is such an amorphous and vague concept that personally I think it's virtually meaningless. Nobody can agree on how to define it or how important it is.