[FOM] Historical notation question

praatika@mappi.helsinki.fi praatika at mappi.helsinki.fi
Wed Feb 25 06:36:02 EST 2004

Brian Postow was asking about the origin of the notation \Sigma_i and \Pi_i 
for the different levels of the arithmetic hierarchy. 

I don't think that Hirst and Sambin really managed to reply this question. 

I can't really confirm this now but I am pretty confident that this 
notation, *for the levels of the arithmetical hierarchy*, is due to John 
Addison (from the late 1950s).



Panu Raatikainen

PhD., Docent in Theoretical Philosophy
Fellow, Helsinki Collegium for Advanced Studies
University of Helsinki
Helsinki Collegium for Advanced Studies
P.O. Box 4
FIN-00014 University of Helsinki

E-mail: panu.raatikainen at helsinki.fi

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