If you want to understand what R. H. Blyth meant by connecting Zen and hokku, it can be stated very simply.
To Blyth, Zen was the elimination of the boundary between self and other, between subject and object. I have said before that a human is the universe “humaning,” and a stone is the universe “stoning.” When we eliminate the distinction between subject and object — which exists because of the notion of a self — then all that exists is a unity.
That is why Blyth makes statements that seem initially to make no sense at all. But if you keep what I just said in mind, then you can understand (at least intellectually) what he is talking about.
For example, He mentions these lines of Keats:
I who still saw the universal sun
Heave his broad shoulder o’er the edge of the world.
Blyth goes on to say of them, “If I lift my shoulder the sun rises; if I lower it, it sinks.”
“If you only think about this kind of statement, it seems crazy beyond all endurance…” he remarks. And indeed it does, because thinking involves the separation of subject and object. But if we abandon thinking for a moment, then there is no self and no other — there is no subject-object distinction. That is why when you raise your shoulder, the “sun” — the universe which manifests as both you and sun — rises, because your shoulder is the sun’s, as is mine, as is that of everyone else in the world.
Of course that is a kind of play on words, because we are using “sun” here as a name for the universe. When you raise your shoulder, the universe raises its shoulder, which is not separate from “your” shoulder, but one and the same. The universe as “man” raises its shoulder.
That is why we can say that one thing manifests the whole universe; nothing is separate from the universe. So when you open your eye, a star opens its eye, because there is no separation between you and the star.
That may sound odd at first, but if you just think of the universe as all of the same substance, the action of one thing is the action of all the rest of the universe manifested in that one thing. That is why in hokku we can say that a single cherry blossom is all of spring.
The other thing to keep in mind about Blyth’s notion of Zen is that it is the complete union of mind and action. He tells us that “A thief running away like mad from a ferocious watch-dog may be a splendid example of Zen.” Why? Because in the thief’s mad running away, there is no separation of thought and action. The thief is the running away.
We all know people who cannot seem to unify mind and action. They are filled with hesitation and uncertainty and equivocating and second thoughts. But in Zen, mind and action just plunge ahead as one. That is why when Blyth talks of Zen action, it is not a matter of morals or ethics. It is just the lack of separation of mind and action.
Don’t take that crudely and unwisely, please, as the “Beats” did, to mean that you may do anything you wish, and that whatever you feel like doing is perfectly fine, no matter how immoral it may seem to others. That is not the way the world works. It is just a description of what Blyth meant by Zen, and I hope it will give you a key to understanding some of his more “difficult” statements in his various works.
If we reduce what I have said here to its minimum and apply it to hokku, then we have — as writers of hokku — to keep in mind that hokku generally eliminates the separation of subject (the writer) and object (what is written about). That is why, for example, in the old hokku
The old pond;
A frog jumps in –
The sound of water.
…there is no “poet” visible. He has become one with the pond, the frog, the sound of water, and all of those are also just one. Nor is there any separation of “thing” and “action.” We could describe the “Old Pond” hokku as one long extended verb. That is the unity of hokku.
If you find that what I have written here makes no sense to you the first time you read it through, it would be helpful to read it again and to ponder it. Once you get it, you will understand a lot of Blyth’s writing that previously may have seemed impenetrable.