In his first two lectures Marshall set the scene for the need and possibility of “going beyond the Bible”. In particular he established that we have in fact felt the need to go beyond Scripture, and so showed the need for principled and understood ways of doing this. He also showed that there is within the Bible a development of doctrine in differing contexts.
In the third lecture he begins to really get to grips with how we may biblically go beyond the Bible. Here he shows that when doctrine develops within Scripture we can identify not merely “diversity” but also “greater maturity”1 (though he resists equating this as an evolution in which later texts are always more advanced).
He also shows that Scripture is in some ways “incomplete” both because the teaching is occasional (that is addressed to specific circumstances) and because far future circumstances are not directly addressed. In showing this he also shows that there is continuity in these changes. Thus, speaking of change and of continuity in change, he is very close to the metaphor of a trajectory (which requires both change and continuity). Marshall uses this metaphor in describing the development of Christology into the Pastoral Epistles as an example of such development within Scripture.2
Finally he claims that “[d]evelopments in doctrine and new understandings after the closing of the canon are inevitable.”3 But in order to affirm the authority of Scripture these must be in continuity with teaching in the Bible and must be discerned in accordance with “the mind of Christ”.