Later, Zheng was older and put Lü Buwei and his mother's new boyfriend to death. He put his mother away as a prisoner as well. Now, Zheng and his helper Li Si ruled Qin. Their ideas are called Legalism. It said that the old ways of doing things were not good: if everyone did as ordered by the ruler and by his laws, things would be much better. The best way to run a country was for the ruler to have all the power. That way, no one would be able to fight or hurt other people. As the ruler of Qin, Zheng liked these ideas; as the ruler of China, he said they would be the only ideas. He made Confucianism and other old ideas against the law. Only the library in his palace (great house) was able to have books with any old ideas or with other people's accounts of history. Everyone else would have to read about Legalism and the accounts of history approved by the Emperor. The First Emperor's men then burned the other books and even killed some of the men who tried to keep them by burying them (putting them under the earth).