In an evening talk, Dogen said,

"The biography of the late Sojo Eisai of Kenninji was written by the vice-minister Akikane, a lay monk. At first he refused to do it saying, 'It should be written by a Confucian scholar, because such scholars forget their own bodies and devote themselves to studying from early childhood. Therefore, there are no mistakes in their writings. For ordinary people, working for the government and social intercourse are their primary concerns; they study on the side. Although there have been some eminent people, there have been mistakes in their writings.'

As I think of this, ancient people forgot their bodies in order to study even non-Buddhist texts."

Also Dogen said,

"The late Sojo Koin said, 'Bodhi-mind is studying the dharma-gate (teaching) of the three-thousand worlds in a single moment of thought, and keeping them in one’s mind. This is called bodhi-mind. To meaninglessly wander around in confusion with a bamboo-hat hanging around one’s neck is called a deed influenced by a demon.'"

In ancient Japan, traveling monks wore bamboo hats hanging around their necks. Koin is saying that to be a monk and not study the dharma is to just run around aimlessly.