Qin Emperor Shi Huangdi used the Legalist idea to unify the China Empire.
Legalists idea entails establishment of laws that will rigidly prescribed punishments for specific behaviors. The idea also states that a rich state and powerful army is needed to ensure domestic stability in the nation.
In conclusion, Qin Emperor Shi Huangdi use the Legalist ideas because he believed that the autocracy was needed to unify China.
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