ataraxis ataraxis /ˌætəˈræksɪs/

noun

1. The absence of mental stress or anxiety  ( ataraxis , heartsease , peacefulness , peace , peace of mind , repose , serenity )
   the absence of mental stress or anxiety
     The serene landscape provided a sense of peace and tranquility.
   The serene landscape provided a sense of peace and tranquility.