". . . for half a century serious scholarship had great difficulty in working its way back to history when dealing with Jesus." (21)This is a common trope in academic writing generally and historical scholarship particularly. But apart from being repetitious for readers, it does no argumentative or conceptual work, and it is self-undermining for at least three reasons.
". . . little was done to advance genuine historical work on Jesus in the years between the wars." (22)
". . . the sense of academic disenfranchisement that serious historians of Jesus have felt for decades . . ." (25n.53)
". . . the detailed historical work has not really been taken with full seriousness." (26)
". . . reflecting viewpoints now abandoned by most serious students of the subject-matter concerned . . ." (32-33)
". . . those very serious scholars who believe that Q is a modern fiction from start to finish . . ." (41)
"One of the most recent serious scholarly works on Q . . ." (42)
"Those who want to continue with serious research on Jesus . . ." (44)
First, "serious" is more or less always used to disqualify certain ideas, works, or scholars so as to suggest a (total or near total) unanimity in scholarly judgment. But "serious" in this usage is merely code for: "except for those who disagree—who, as quacks, do not count—everyone agrees." Which, it should not need to be pointed out, is a false unanimity. In this way "serious" is merely synonymous for "good," which often as not is synonymous with "in agreement with me." But then why not be clearer in one's evaluative judgment rather than adverting to the pseudo-neutral "serious"?
Second, where "serious" isn't meant to signify agreement or unanimity, it suggests those who "matter" or "count." But this implies an elitism that scholars, or at least Christian scholars, should repudiate. So what if scholar X or Y isn't at an Oxbridge or Ivy League school? So what if s/he isn't well published or renowned? That fact alone doesn't bear any relation to the quality of his/her work.
Third, the alternative to elitism is the elevation of consensus over contention. That is, "serious" functions rhetorically to say that "most/all real/good scholars agree on X or Y," which in turn suggests that consensus implies the truth of a position. But this is almost always said in the context of an argument for a position that is itself not accepted by most scholars. So which is it? Either: if (most) everybody agrees, we should agree too; or: in spite of (most) everybody agreeing, we should swim against the tide. One can't have it both ways.
In short, "serious" as a qualifier hides judgments that require arguments to support them. It's an argumentative dodge and a rhetorical shortcut that functions to dismiss a position that one hasn't put in the work to reject. It's a bad habit that truly serious scholars should kick.