The Qin Dynasty. 221 B.C. – 206 B.C.; Shi Huangdi (Shi Huang-ti). 1- first Qin ruler. 2- expanded empire. 3- believed in Legalism (Chinese philosophy). a) believed in strong rulers and harsh punishments. people are selfish and will only obey if afraid of ruler's power. 4- united previous walls into a Great Wall of China.