"Think nonthinking" is a phrase by Dogen that people stumble over and find confusing. People in Dogen's time, and even now, misunderstand it to mean "don't think." A better translation of "Non Thinking" is "just think." Like, "just sit," this is not a simple phrase. Our thinking is not something contaminating our mind, something we're trying to get rid of. We let it be there empty of intention. Let thought just be thought, not something we have to do anything about whatsoever.