unimpassioned
adjective
un·im·pas·sioned ˌən-im-ˈpa-shənd 
: not impassioned
especially : marked by calm reasonableness
an unimpassioned discussion of the problem
… she was thinking over her situation … in a deliberate and unimpassioned manner … 
Henry James
Henry James 
Word History
First Known Use
1744, in the meaning defined above