Using Professor Rodes’ midpoint theory, let’s take a look at Measure for Measure.
There are 2594 lines in in the play, which means the midpoint is at line 1297, or at Act Three, Scene One, line 191. According to Dr. Rodes’ theory, you could find at this midpoint (or within twenty lines either way) a speech that perfectly sums up a major theme of the play. The 20-line leeway was to help remove the differences in prose line lengths between individual editions. Of course, with over 40% of this play in prose, we may need to expand that leeway.
The midpoint proper comes when the duke, disguised as the friar, talks to Isabella after he hears of Angelo’s abuse of power and proposition of Isabella. The fruke has asked what she is willing to do to save her brother and bring down Angelo, and she responds that she will denounce the deputy before the duke upon his arrival, no matter that she “will open (her) lips in vain” (III.i.191).
As in the last play, All’s Well That Ends Well, this midpoint appears to be merely a narrative pivot point, as it occurs when the duke reveals the plot that will consume the second half of the play, the Bed Trick, and Angelo’s downfall. However, there’s so much more here.
In the speech that precedes this one, the duke references Angelo for the first time since learning of the proposition, calling him “this substitute” (III.i.185). This is a mere 6 lines away from our midpoint.
Within roughly a hundred lines either way of the midpoint, we get five uses of the word “deputy” (III.i.88, III.i.252, III.ii.16, III.ii.32, and 34), over a quarter of all such references in the play.
Within this span of lines we also get an additional two (fitting) references: “combinate” (III.i.220), meaning “betrothed, promised, settled by contract” but also, and more importantly, “combined” (“combinate, adj.; b and a, respectively” Oxford English Dictionary Online. Oxford University Press, September 2015. Web. 20 November 2015.); and “doubleness” (III.i.254).
Substitute. Deputy. Combinate. Doubleness.
Add to this a reference to another plot parallel (Isabella in peril because of her brother Claudio; and the fruke’s story of Mariana’s lost brother and dowry), and you have a recurring thematic motif of seconds and doubles.
I said a couple of days back when discussing the wider use of “substitute” and “deputy” in Measure for Measure compared to the other plays of the Canon, that this idea of doubles might be a key to the play.
This–and Professor Rodes’ theory–make this conclusion almost undeniable.