Hagner addresses firstly the age-old debate on whether it is more accurate to speak of Paul's new Christian identity as a call or a conversion (101-102). Hagner astutely points out that if one speaks of Paul's encounter with the risen Lord as a 'call' displays continuity with Judaism, while Paul's 'conversion' emphasizes a break with Judaism.
One of the strengths of Hagner's overall treatment in this essay is on display here. He avoids easy solutions to this complex situation and posits, rightly in my view, that both 'call' and 'conversion' are both true and to separate them is to create an 'artificial dichotomy' (101).
Hagner points out that for Paul using the term "called" locates his experience as akin to the prophets calling (e.g. Isa 49.1; Jer 1.5; cf. Gal 1.15-16; Rom 1.1; 102). Christianity for Paul is not a change from one religion to the other, but rather is the fulfillment of his Jewish faith.
'Conversion' is also an apt description of Paul's experience, in that there exists a dramatic enough shift in Paul's perspective on Judaism to render his experience in this manner. As Hagner demonstrates, Paul speaks of his life in Judaism as something he left behind (e.g. Gal 1.13-14; Phil 3.7-9). Hagner ends this section stating:
There is sufficient discontinuity in this shift in allegiance from Torah to Christ to warrant speaking also of a conversion of Paul. Paul has not changed religions, but he now has a new center--the crucified and resurrected Messiah, who has inaugurated a new era in salvation history and brought a new dynamic to his existence. He could no longer felt comfortable in his former Judaism. (102)