Ataraxia, untroubledness, is the calm of a mind free from fear and anxiety. The Epicureans sought it by understanding nature and limiting desires; the Pyrrhonian Sceptics by suspending judgement, which, they said, tranquillity follows as a shadow follows a body.
Ataraxia
Tranquillity: freedom from disturbance, the goal of Epicurean and Sceptic philosophy.
Also: tranquillity