Bashō's verse admires the person who sees lightning and does not take the flash for enlightenment. Lightning is one of Buddhism's oldest pictures of how quickly everything passes. A fashionable Zen of Bashō's day felt a small thrill of insight at every flash, and called the thrill awakening. The verse praises the one who lets lightning be lightning. Bashō meant it for his own students, whose easy Zen he was scolding. Its readers agree on that much and differ only in flavor. Some hear a rebuke to shallow Zen. Some hear a plain statement that life is life and lightning is lightning, and some a wariness of enlightenment itself. Which you hear is yours.
The last word, 貴さよ, is read tattosa yo. That is how Bashō's own letter spells it and how the modern complete editions print it; translators working from the printed text give tōtosa yo.
The English is Robert Hass's, from his The Essential Haiku of 1994.
Bashō's own letter to Kyokusui, dated the sixth day of the ninth month of Genroku 3 (1690) and written at Gichū-ji on Lake Biwa, records the verse in the poet's own hand, under a Zen teacher's warning he sets down there.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 稲妻にさとらぬ人の貴さよ.