Let me offer the little book "Second Thoughts" as evidence as 
to mccloskey's use of rhetoric as a weapon, and the concept 
of knowledge as a thing.  First page, says it's essays by 
professional historians on critical topics.  But every author has 
a Ph.D. in economics, not history, though they happen to write 
on economic history.  Few of the essays shows any familiarity 
with the historiography on the issues.  None of the essays would 
point the reader toward that historiography.  In each case, more 
so in some than others, a "problem" is "solved" due to "good 
sound thinking" -- a rather narrow neoclassical approach that does 
as little justice to the subdisciplinary specialties in economics 
as it does to the historiography.  In short, there is no acknowledgement 
at all that gosh gee, there might be other scholars with a different 
take on this and it might NOT be because they're just not as smart. 
 
If McCloskey, who wrote the book, uses rhetoric in this way, don't 
be surprised if economists who read the book think one can use 
rhetoric this way. 
 
As for the Greeks, well, every conversation on the 'net, at a seminar 
or otherwise that I have had with Prof. McCloskey on this issue 
has ALWAYS ended up with the perfesser referring to the Greeks as 
the last word on the subject.  So that's how they come in. 
 
As for your comment about historiography.  I was dually trained 
in econ and history, but my Ph.D. is in history at Johns Hopkins. 
I recall friends who were econ grad students at the time asking 
me, in pure naivete and sincerity, what I could possibly LEARN 
in history graduate school.  What could they possibly TEACH. 
 
Well, what they teach (or should -- some departments, after all, 
are better than others) is knowledge of and respect for the 
historiography, the long conversation of past, present and future. 
knowledge of and respect for sources.  And my own advisor, Jack 
Greene, did indeed take seriously the practice of our "craft", 
as he called it, meaning how well we wrote.   
 
I do think that graduate students in history could probably 
benefit from a more conscious approach to the teaching of 
rhetoric, analysis, logic, fallacies.  But that happens in a 
good school in the context of the seminar, when you give papers 
and your colleagues critique them, when you and your fellow 
students discuss different interpretive works.   
 
Truthfully, the arrogance of asserting that someone trained 
in an economics department is going to know more about 
EVERYTHING than anyone trained in a different discipline -- 
particularly someone trained at one of the top programs in 
that discipline in the country.  Oh please.         
 
But in a way it's a good example of what I mean.  In a way, 
a rather perverse way, McCloskey has left too many economists 
thinking that all they have to do is read his books, and then 
they know all there is to know about rhetoric, argument, 
narrative.   
 
Mary Schweitzer