Complex sentence: Afterwards he became a recluse, studying Buddhism and Daoism, and at this time began to have his first doubts over Zhu Xi's philosophy, even changing his pen name which showed his commitment to humaneness ("jin").
Split into simpler sentences: Afterwards he became a recluse, studying Buddhism and Daoism. During this time he began to have his first doubts over Zhu Xi's philosophy, even changing his pen name which showed his commitment to humaneness ("jin").