Hayek observed that  ?nobody can be a great economist who is only an
economist?and I am tempted to add that the economist who is only an
economist is likely to become a nuisance if not a positive danger?
(1956, p. 463).

Which 1956 book by Hayek is this from?

Hello.

The 1956 book that you're seeking is "The State of the Social
Sciences," edited by Leonard White. Chicago: U. of Chicago Press.

As my friend and colleague Bobbie7 notes below, the quotation is from
Hayek's "The Dilemma of Specialization," which was republished in 1967
in "Studies in Philosophy, Politics and Economics"  Also see:
http://www.eh.net/pipermail/hes/2002-January/001798.html

"The Dilemma of Specialization" was originally published in "The State
of the Social Sciences" (1956).

See:
"Hayek, F. A.  1956.  "The Dilemma of Specialization".  In The State
of the Social Sciences, edited by Leonard White. Chicago: U. of
Chicago Press."
source: hayekcenter.org
http://www.hayekcenter.org/friedrichhayek/hbib59-50.html#1956

Bibliographic data for "The State of the Social Sciences" at the
Library of Congress:
http://catalog.loc.gov/cgi-bin/Pwebrecon.cgi?v3=1&DB=local&CMD=010a+56009131&CNT=10+records+per+page

As indicated in the bibliographic data, the book was a collection of
papers presented at the 25th anniversary of the Social Science
Research Building at the University of Chicago, November 10-12, 1955. 
Hayek's "The Dilemma of Specialization" is one of the papers in the
book.

Used copies at Abebooks.com:
http://dogbert.abebooks.com/servlet/SearchResults?imagefield.x=0&an=white&tn=state+of+the+social+sciences&imagefield.y=0

---------
search strategy:
hayek "economist is likely to become a nuisance"
hayek "dilemma of specialization"
"State of the Social Sciences" white 

I hope this helps.

Would this information meet your needs?


Friedrich August von Hayek (1899-1992)

"The physicist who is only a physicist can still be a first-class
physicist and a most valuable member of society. But nobody can be a
great economist who is only an economist - and I am even tempted to
add that the economist who is only an economist is likely to become a
nuisance if not a positive danger."

Source: The Dilemma of Specialization' in Studies in Philosophy,
Politics and Economics, 1967, p. 123.
http://prawo.uni.wroc.pl/~kwasnicki/cytaty_ekonomia.htm

Thanks,
Bobbie7