Is Dogen’s understanding of meditation (zazen, shikantaza) the same as that of the Sixth Patriarch Hui-neng’s? The answer is, no. Here is what Hui-neng had to say about meditation:
“Now that we know that this is so, what is it in this teaching that we call ‘siting in meditation’ (tso-ch’an)? In this teaching ‘sitting’ means without any obstruction anywhere, outwardly and under all circumstances, not to activate thoughts. ‘Meditation’ is internally to see the original nature and not become confused” (trans. Yampolsky).
What we notice right away is that the Sixth Patriarch’s zazen (tso-ch’an) is not to be taken literally. By comparison, for Dogen the posture seems to be everything. He wants us to understand that the concrete act of sitting, itself, is the true Buddhist practice and accomplishment. Dogen, in his great work, Shobogenzo, even speaks of a "one-to-one Transmission of the seated meditation of Buddha" when there is nothing of the sort in Buddhism to be found. It is instructive to point out that the, so-called, Zen transmission is Mind to Mind not zazen to zazen.
Can any Zennist doubt that Mind (the Buddha Mind) transcends physical existence including physical postures such as sitting? Why then does Dogen insist that physical sitting is primary? He even says in the Shobogenzo:
“Truly, you need to recognize that a beginner’s meditation is their first time of doing seated meditation, and that one’s first time of doing seated meditation is the first instance of being seated Buddha.” (On Wanshi’s ‘Kindly Advice for Doing Seated Meditation')
The physical act of sitting doesn’t make anyone a Buddha even in a Zen temple or monastery. The Buddha—the true Buddha—is not known by physical characteristics. Doesn’t Dogen read the canon? “O Ananda, the [real] Buddha is indemonstrable. He cannot be seen by the eye" (Sthira-adhyâshaya-parivarta Sutra).
To paraphrase Carl Bielefeldt (Dogen’s Manuals of Zen Meditation), it is not amazing for any great teacher of Zen to teach that Zen is about realizing Buddha Mind. What would be amazing is to teach that the concrete exercise of zazen is the way to realize this Mind. Here does one have to part company with Dogen and his understanding of Buddhism—especially Zen. It is far too heterodox.