Regarding Kavanaugh's speculation that the availability of the Bible and other religious material in print encouraged the understanding of church services as instructional it seems that the opposite should have been the case. With widespread literacy and the ready availability of Bibles and other religious books one would think that there was less motivation to use church services for instruction--people could read the stuff at home.
Along these lines here's a heretical thought: maybe sermons should be abolished. Given virtually universal literacy (in developed countries) and ready access to information through printed media and the internet, do we need sermons? If so, for what?