J. Eric Butler wrote:
As an academic in a humanities discipline, I read a lot of formal prose concerning historical subjects. I often come across the English future perfect in these contexts, which strikes me as odd, albeit easy enough to understand. So I usually just barely register it and then move on. But at some point it occurred to me that I have no idea what motivates this usage, so I thought LL would probably have some insight.
Here's some actual examples of this usage "in the wild":
"We cannot claim that this is an exhaustive list of the political functions of the Areopagus in the archaic state. Its mandate will have been wider and vaguer than our scant evidence permits us to reconstruct." (Ostwald, From Popular Sovereignty to the Sovereignty of Law)
"Even if he did make for the coast from Babaeski east of Edirne (which seems less likely, since he had severed contact with his fleet until he reached the Danube), the journey will have been not much shorter." (Cawkwell, The Greek Wars: The Failure of Persia)
"And here too, reinterpretation of the Clouds parabasis both casts new light upon the attitude of Aristophanes towards politically oriented poetic rivals like Eupolis, and also reveals the possible existence of a satirical method – metacomedy – which brings into play a whole swathe of lost dramas by competitors which will have been reused, in full expectation of audience recognition, in order to subvert and satirise rival poets’ earlier political satires." (Sidwell, Aristophanes the Democrat)
"The case will have been heard after 357/6, the earliest year in which joint trierarchies (cf. 7.38) are known. The most likely date is the spring of 354" (Gagarin, Introduction to Isaeus 7, in Speeches from Athenian Law)
Eric ends this way:
I don't have access to The Cambridge Grammar of the English Language, but none of the English usage sources I do have seem aware of this usage. If it's not in CGEL, do you think Huddleston and Pullum will let me name it? ;-)
I suspect that Huddleston and Pullum would be better disposed towards this option if Eric bought a copy of the book. But in fact, I'm so distracted by the idea of "naming rights" for syntactic constructions that I'm having a hard time focusing on his original question — once the bidding starts, I doubt that J. Eric Butler will be able to compete. This one, for example, might end up as "the BNY Mellon Future Perfect of Historical Speculation". (Though, as we'll see, it's neither future nor perfect…) And there are hundreds of these naming opportunities — thousands, if we include things like "the Dodge Charger Northern Cities Shift", or "Positive Anymore Presented by New York Life".
Turning regretfully away from this visionary solution to the LSA's money troubles, I'll only note that the usage pattern at issue is consistent with CGEL's argument that "will [...] is an auxiliary of mood, not tense" (pp. 208-210):
The difference in interpretation between a simple present tense and its counterpart with will is to a very large extent a matter of modality. Compare, for example:
|PRESENT TIME||FUTURE TIME|
|SIMPLE PRESENT||That is the doctor.||They meet in the final in May.|
|will + PLAIN FORM||That will be the doctor.||They will meet in the final in May.|
In each pair the time is the same, but the version with will is epistemically weaker than the simple present.
Note that J.E.B.'s examples all deal with past time. And as Rodney Huddleston has pointed out (P.C.), this suggests that just as the will here indicates epistemic modality rather than future time, so the have indicates past time, rather than perfective aspect:
"He will have told her yesterday" is the modalised version of "He told her yesterday".
But "the will of Epistemic Weakening" is not so attractive as a naming opportunity. Maybe "the will of Optimal Inference"?
Update — I should add that similar modal uses of "will have been" are common in the natural sciences and mathematics as well, e.g.
Some regions are likely to be more reliable than others. For example, regions in the core of the protein will tend to have more clearly defined electron densities and so will have been easier to interpret during the determination of the structure.
For this reason the reader cannot be sure what to expect when he turns to the entry that interests him, beyond knowing that the article will have been written by someone with first-hand experience and some authority.
These faulty spectra remain in the refined second edition. To a high probability most of these problems will have been caused by interference, either affecting the temperature scale or the profile shape with spurious components.
[H]owever, there is far more in it than can be covered in a single degree course, and its main usefulness may well be as a reference book for postgraduate students who need to know more algebra than they will have been formally taught.
(Despite the use of have, note that with the partial exception of the third example, these all deal with inferences about a hypothetical sequence of events, rather than inferences about the placement or nature of events with respect to a concrete past time-line.)
See also "That would be in the modal auxiliary, Bob", 1/9/2008; "We've met the enemy, and that would be in the modal auxiliary, Bob", 3/18/2009; "Why 'That would be me' (part 1)", 4/2/2009; "Why 'That would be me' (part 2)", 4/3/2009.