In all his voluminous writings, so far as I’m aware, Master Dogen only makes a statement about Enlightenment once. And significantly he makes that not to his monks but to a lay follower. In the Genjokoan he says:
To carry the self forward to experience the myriad things is delusion. That myriad things come forth and illuminate the self is Awakening.
Genjōkōan, Dogen
To understand this we need to understand the word for self, “jiko’’, has two distinct meanings. One is self in the ordinary sense – the ego self. And the other is the big self of everything – of which the little self is a part – the whole universe. So if we paraphrase this statement it would be something like:
To carry my self forward to experience things is delusion. To allow each thing to manifest itself is Enlightenment.
Quintessentially of course, Dogen is always talking about our experience in zazen. And in zazen, this person of practice is the Cave of the whole world, illuminated.