Scholars continue to debate the interpretation of πίστις Χριστοῦ—it can be translated either “faith in Christ” or “[the] faith [or faithfulness] of Christ.” (A recent book on various aspects of this issue is The Faith of Jesus Christ: Exegetical, Biblical, and Theological Studies, edited by Michael Bird and Preston Sprinkle.)
Related to this debate is an interesting new article by F. Gerald Downing: “Ambiguity, Ancient Semantics, and Faith,” NTS 56 (2010): 139-162.
He begins by noting that “It is hard to find a contemporary scholar actually approving sustained ambiguity in the interpretation of ancient texts, especially in the πίστις Χριστοῦ debate” (139). Downing does not actually example the phrase in-depth, but rather looks at the larger issue of polysemity and the ancient understanding of ambiguity, “semantic richness,” and “lexcial flexibility.”
A few quotes for those who might be interested.
On ancient rhetoric:
The pragmatics of ancient rhetoric was discursive. It shows no sign of normally relying, let alone normally insisting on fine distinctions of meaning. (p. 17)
On expectations of ancient authors:
To read ancient authors as though they ‘must’ have shared the concern evinced by some among us for connotative precision risks making a category mistake, a mistake in the genre of verbal articulation deployed. (p. 146; italics his)
On how words work, then and now:
Words, then as today, work precisely because their connotations allow them to be used in many settings, and to seem to speakers and hearers to sit comfortably and ‘at home’ where the speaker has settled them, with the context likely foregrounding some connotation(s), but mostly without that speaker feeling any need or desire either to purge or to impoverish the utterance by explicitly exiling others. (p. 162)
On the complexity of human language, and how the normal language process does not preclude a range of connotations:
This is, again, not to suggest that the ancients’ brains worked differently. It is very unlikely that any major genetic change has occurred over just two millennia. The human language function then was surely just as complex as it is today, as complex as is taken for granted in current debates over psycholinguistics. Rather would it seem likely that ‘[h]umans behave like jugglers when they use the mental lexicon, in that they have to deal with semantic, syntactic and phonological information at the same time’. In current discussion there seems to be no suggestion that in the midst of this juggling, between initial inchoate thought and final articulation, there is included a process of checking the range of connotations of each word—or even each leading word—and then preparing to ensure a context (itself also comprehensively scrutinised) that should implicitly preclude every undesired or potentially distracting sense for each term judged important. For sure, we are able to monitor and explicitly to correct our speech just prior to utterance, or soon after; and our writing more readily still, especially with the help of computers. But there seems to be no empirical evidence for any prior weeding-out of nuances of words as a part of natural language production, today, or, a fortiori, back then. (p. 23)
On why “faith in” already implies the “faithfulness of” the object:
In Paul’s world, trust in someone was itself founded in, and displayed and presupposed belief in their trustworthiness (as well as, most likely, their willingness to trust you): faith in Jesus would necessarily imply (unless explicitly denied) at the least a trust in his faithfulness. Ancient expectations of words have them carry much of their semantic baggage with them, whatever part of their range appears in context to be foregrounded; that is, unless some elements of their range have been specifically discarded. Taking into account ancient understandings of how language works, and noting ancient usage of the key vocabulary, and failing any explicit exclusions from the semantic field of πίστις, the faithfulness of the one trusted is inevitably also there, in the picture, albeit in softer focus. (p. 160)