Page "Korean philosophy" Paragraph 13

Every major Korean neo-Confucianist shared Toegye's preoccupation with single-mindedness, which signalled new stress on praxis in the development of Korean neo-Confucianism: the fusion of the metaphysical and the physical is better brought about through action than speculation, important as theory might be.

That was the point of Yulgok's integration of sincerity ( sung ) with single-mindedness.

In this respect Korean neo-Confucianism made a break with the Cheng-Chu school of Chinese neo-Confucianism, which was overly speculative.