Dogen continues bouncing from one viewpoint to the other in the next passage of Genjo Koan, the third fascicle of the Shobogenzo:
Driving ourselves to practice and experience potential is delusion. When potential actively practices and experiences us, that is the state of realization.
Those who realize their delusion are buddhas. Ordinary beings are those who are deluded about realization.
But there are also people who realize potential on the basis of realization, and there are people who fall deeper into delusion due to their own delusions.
Those buddhas who realize potential do not consider themselves to be buddhas. Nevertheless, they are buddhas as they continue to experience potential.
I've taken a lot of liberties with my interpretation. I encourage the interested reader to compare my interpretation with any of the fine translations out there to get a better sense both of what Dogen was saying and what I mean.
Dogen's first lines above contrast the relative and the absolute: it is delusional to think that potential is a thing that can be grasped and attained, that it is a "thing" at all (the relative view). Dogen contrasts that with the absolute view, a realization that everything always was and always will be potential, that we arise from potential, not the other way around.
The next pair of lines are playfully transcendental: those who realize they are deluded are awakened, and those who think that they are awakened are actually deluded. But before we get stuck thinking "black is white and white is black," Dogen mixes it up in the next lines and says there are those who are awakened to their awakening and those who are deluded by their own delusions ("black is black and white is white").
The closing lines express the practical viewpoint, and resolve the previous lines: since in potential there is no differentiation between this or that, between self or other, those experiencing the state of potential do not think of themselves as "buddhas" or "awakened," or for that matter, as "selves." Yet it is in this state, Dogen points out, that they are in fact buddhas.
This raises the question, if those experiencing the state of potential do not think of themselves as buddhas, or even as selves, what do they think? Can this question even be answered, as any answer will by necessity involve trying to imagine or reify potential and realization, which Dogen points out is actually delusion.
However, the answer can be experienced. In order to experience the answer, sit comfortably someplace and focus your attention on your breath. Breathing slowly but naturally, count "one," then "two," and so on with each exhalation until you get to ten, and then start the count over again. Do this for 10 minutes.