I am glad that you asked for "additional authority or insight" and not
for a definitive answer to your question, because there is no
definitive answer to how the adjectival forms of the names Coase and
Pigou (or most of the untold number of similar adjectival
constructions) should be spelled. But let me try to add some of the
"additional authority and insight" that you request regarding this
very interesting problem. Let's start with a useful generalization:
To paraphrase Duke Ellington's definition of good music, which is "if
it sounds good, it is good," the rule of thumb for choosing among
suffixes to turn proper names into adjectives is that, all else being
equal, "if it sounds good, it is spelled correctly."
As R. W. Burchfield describes the history of this adjectival form in
the Fowler's excerpt you reference in your question, "[t]he choice of
suffix seems to have been mostly governed by euphony." "Modern
English Usage," 4th Edition, R.W. Burchfield, ed., Oxford (1998), p.
The main reason for the lack of prescriptive rules governing these
constructions is that most of them are invented by academics and
journalists, and they come into being and go out of the language as
intellectual and popular fashions change. Slate.com offers the maxim
"[u]se it if sounds right" as a way to deal with the "adjectival use
of authors' and artists' names [that] is proliferating in newspapers
Slate.com: The Daily Digest of Arts and Argument: "Portrait of the
Author as an Adjective" (about 7/8 down the page)
Having stated this general principle, let me try to offer some useful
guidance on the two examples you have cited (although I think that the
Coasean/Coasian situation is much more interesting and difficult than
the Pigouvian/Pigovian example).
The Compact Edition of the Oxford English Dictionary, Oxford
University Press (1971)("OED") has an entry for the suffix "-an" (at
page 75) and one for "-ian" (at page 1364). The OED's entry for "-an"
describes "-ian" as "merely a euphonic variety of '-an'", citing
"Christian" and "Corinthian" as examples. The OED's separate entry for
"-ian" cites it as being used in "modern formations from proper names,
the number of which is without limit," and lists a few dozen examples,
including Wordsworthian, Johnsonian and Tennysonian.
The OED has no entry for "-ean". And, interestingly, the Fowler's
entry cited above makes no mention of "-ean" as an alternative to
"-ian" and the only examples cited of this construction are
"Aeschylean" (about which, see below) and "Brontéan," in the latter
case presumably because of the accent mark.
From this we can reasonably conclude that the "standard" form of this
suffix is "-ian," and that "-ean" can usefully be considered only as
an exception to the "rule." So, when, if ever, should "-ean" be
considered the preferred (as opposed to an "acceptable" alternative)
spelling of this suffix?
There is authority for the proposition that "-ean" should be used when
the name has the typically Greek ending of "-es" Representative
examples include Hercules ("Herculean") and Procrustes ("Procrustean")
. "American Heritage Dictionary of the English Language," Fourth
Edition, Houghton Mifflin (2000).
Another much narrower class of exceptions might be drawn for
adjectival forms of names that are naturally pronounced with an accent
on the first syllable of the suffix. Two examples from the OED of
this construction are Aristotelean (OED, page 112) and Mephistophelean
(OED, page 1771). (In both cases, the OED would also allow an "-ian"
suffix, but only if the accent is moved back to the previous
syllable.) Another example of this construction is "Aeschylean" (from
"Aechylus"), which the American Heritage Dictionary says must be
pronounced with an accent on the final "e".
Finally, there is some style-book authority for the proposition that
an "-ean" suffix may be preferred if it more closely tracks the
original form of the word. The most common example of this may be
"Shakespearean." This seems to me to be more common that
"Shakespearian," although both versions are cited as acceptable by the
American Heritage Dictionary and the OED. One onlinesource states:
"Possessives formed from proper names should follow as closely as
possible the original name (Shakespearean [not -ian], but Chomskian,
Oxford University Publishing: Style Notes For Contributors: The
English Association: University of Leicester (at page 4 of PDF
My conclusion from all of the above that "Coasian" is preferable to
"Coasean," although the latter may be plausibly justified as being
more aligned with the original form of Dr. Coase's name.
It seems to me that this is a much easier case. The addition of the
"v" for pronounceability is conventional and uncontroversial (e.g.,
"Shavian, Thoreauvian). The only issue seems to be whether the "u"
should be dropped in the adjectival form of Dr. Pigou's name. And,
from my research, the only reason to do that would be to enhance the
pronounceability of the adjective or to track more closely the
spelling or pronunciation of the economist's name. "Pigovian" does
According to the Infoplease.com online encyclopedia (and other
sources), Dr. Arthur C. Pigou's last name is pronounced "pi-GOO."
Infoplease.com: Encyclopedia: Arthur C. Pigou
Presumably, the spelling of "Pigovian" is driven by the notion that a
"v" should replace the "u" instead of being added to it in creating
the adjectival form. This would be consistent with the "Shavian"
example (which Latinizes the "w" into a "v"), but not the
Most important, it is natural to pronounce "Pigovian" with a long "o"
that is entirely different from the vowel sound in Pigou. On the
other hand, it is entirely natural, and not at all awkward, to
pronounce "Pigouvian" with the same "oo" sound as that of the
Under the circumstances, I suggest that "Pigouvian" is deservedly the
I used print resources from my home library, as well as various Google
searches, including the following:
suffix OR suffixes ean ian
spelled ian ean
adjectives ian ean
This was a fascinating question to research, and I hope that you are
satisfied with the "additional authority or insight" that I was able
to provide. If any of the above is unclear, please ask for
clarification before rating this answer.