Hi David,

How about:

"Observed facts are necessarily finite in number; possible 
hypotheses, infinite. If there is one hypothesis that is consistent 
with the available evidence, there are always an infinite number that are."
P.9 of Friedman, M. (1953). The methodology of positive economics. In 
M. Friedman (Ed.), Essays in positive economics (pp. 3-43). Chicago, 
Ill.: University of Chicago Press

(Shorten the second quote to just the first sentence, or cut any of 
the others. The first could go as it says something related to this.)

Regards,

Stuart Birks