1. William James, Textbook of Psychology (London: Macmillan, 1892), pp. 12–13.
2. Katsuki Sekida, in Zen Training (New York and Tokyo: Weatherhill, Inc., 1975), pp. 47–52, goes into this phenomenon of the tension in the tanden stimulating the cortex in great detail; in doing so, Sekida also draws from Arthur C. Guyton, Function of the Human Body (Philadelphia and London: Saunders, 1959), pp. 370–72.
3. This figure and the account of normal respiration are adapted, with modifications, from Arthur C. Guyton, Function of the Human Body, pp. 220–21.
4. In the original work, the author goes into fascinating detail: “The kanna Zen (working on koans) of the Rinzai sect involves a large element of positive samadhi (although training in absolute samadhi is also found in this school), while in the practice of shikantaza of the Soto school, absolute samadhi is more important (though of course here, too, positive samadhi is developed as well).” Zen Training, p. 62.
And later he adds, “It seems likely that the two types of samadhi are correlated with distinctly different patterns of electrical activity in the brain,” and refers to various studies in India and Japan. Zen Training, p. 63.
5. See the Glossary for a more complete definition of kensho. For much greater depth, see Katsuki Sekida’s Zen Training. There is an entire chapter called “Kensho Experiences.”
6. This poem is from Case 5 of the Hekigan Roku. The entire book of koans has been brilliantly translated with commentaries by Katsuki Sekida in his great work Two Zen Classics.
7. In Zen Training (p. 163), Katsuki Sekida comments: “‘Thrownness’ is a term that appears in Heidegger’s Being and Time. No one seems to take it as a disease and an object of possible remedy.” One time in conversation, Sekida said (this is paraphrased — probably inaccurately — from memory), “Western philosophers, especially the Existentialists, have discovered Buddha’s First Great Truth: life is suffering, life is basically unsatisfactory, filled with anxiety. But they haven’t gone beyond that, to see there is a state beyond suffering.” In other words, they haven’t discovered the other three Great Truths of the Buddha. In Zen, we study all four of Buddha’s greatest insights: the truth of suffering, its causes, its cessation, and the path to its cessation. In doing so, we go beyond “thrownness.”
8. Hekigan Roku, Case 94. Quoted from Two Zen Classics, translated and with commentaries by Katsuki Sekida.
9. Katsuki Sekida writes in Zen Training (p. 174): “Jo Hoshi (A.D. 382–414) was a genius as a Buddhist scholar. He is said to have met an untimely death by execution when, for religious reasons, he refused to obey an order of the ruler of the state. According to legend, his farewell poem was as follows:
The four elements have originally no master;
The five aggregates are essentially empty.
Now my head meets the sword;
Let’s do it like hewing the spring breeze.
Sekida adds: “On another occasion, Jo wrote, ‘The person who has exhausted truth is vast and void, and leaves no trace. All things are one’s own making. Those who realize all things as themselves are none other than sages.’”
10. This description includes words from one of the kensho experiences Katsuki Sekida writes about in Zen Training (pp. 158–59). He has obviously written from direct experience. Earlier in the book, Sekida wrote that perhaps someday a genius of Zen would appear to be able to describe the Zen experience in writing. I believe he was being modest; this passage as well as many others in his work is in my opinion the work of genius.