About (a) "interaction among distinctly human actors," (b) that 
economists before Mises had not clearly identified them, and (c) 
economics as Wissenschaft: Does Adolph Wagner (1835-1917) count as an 
economist here? I suppose the mature Mises did not think so. But see 
Veblen's review in the Journal of Political Economy, I, 1 (1892). And 
was it not Wagner who made Menger acceptable to the "historical 
school" (despite Schmoller)?

Anyway, it is certainly true that he distinguished between 
menschliche Handeln (human interaction) and wirthschaftliche Handeln 
(economic interaction). See for example his Grundlegung der 
politischen Oekonomie (1892).

For that matter, the same distinction, already classic for Wagner, 
see the preface to Menger's Grundsaetze der Volkswirthschaftslehre 
(1871), online thanks to the German Mises website: 
http://docs.mises.de/Menger/Menger_Grundsaetze.pdf .

It would be interesting to know how Mises wrote of Handeln and 
Handlungen before English translations of his  work began to appear, 
and how he came to translate Wissenschaft as simply "science," or if 
he actually did, and if not, who did.

John Womack