This is a groundbreaking work. I don't say that lightly, or as a throw around description. I say that because Bonner has demonstrated that Pelagianism as a school of thought or as some novel movement is a myth and, as such, she argues that it is not historical responsible to continue using the term 'Pelagian' or 'semi-Pelagian' to designate a theological category. The most compelling reason for this, in my mind, is her work which demonstrates that Pelagius's teachings really are in the ascetic parenesis of such authors as Athanasius and Evagrius and the early Jerome so, her reasoning goes, if we are to condemn Pelagius as a heretic, we have to condemn the long line of ascetic teachers whom he follows after as well.
However, as an analogy, Brian Daley's fantastic work, God Visible, shows how many statements of the early church fathers prior to the Nicene settlement (if you will) could be seen as falling into one of the categories of heresy. Now, it could be said that prior to Nicaea, these church fathers simply hadn't fully worked out their Christology and as such we should cut them some slack but if they were to make the same unguarded or careless assertions post-Nicaea, then they would be deemed a heretic. I think the same could apply to the ascetic tendencies of church fathers, of which Pelagius is an heir. With some darkness of understanding, Athanasius endorsed something approximating what is now known as 'Pelagianism' but we would cut him some slack but if any, after these matters were clarified with Augustine, were to advocate for these positions, then they would deemed heretical. The recognition that the church continues to discover theological truth ought not to be considered out of bounds nor ought said development be ignored, effectively allowing heretical teachings to be endorsed as within proper orthodox boundaries.
Despite this aside, Bonner's work is an excellent example of careful and clear historical scholarship.