Wikipedia offers the following, but I'd be a bit wary about relying on it. You might find some detailed papers on the net. (It's his most famous poem, but I suspect his other stuff gets more academic attention.)
Wikipedia Wrote:Miyazawa chose to write the poem using katakana. This is stylistically odd from a modern perspective,[citation needed] as katakana is nowadays (usually) only used in Japanese writing to denote foreign words. However, at the time, katakana rather than hiragana was the preferred syllabary. The limited use of kanji might be viewed as a move to make his poem more accessible to the rural folk of northern Japan with whom he spent his life,[citation needed] or perhaps as similar to American poet e. e. cummings's style in using primarily lower case.[citation needed]
I wouldn't say katakana was the preferred syllabary in 1930. Katakana-only wasn't used. Kanji & katakana were still used in official documents then, but popular stuff was in kanji & hiragana and had been for a long time. Even during the Edo period, some popular books were published using mostly hiragana with some kanji with furigana for those with poor reading skills. Katakana was sometimes used as a phonetic guide for kanji ateji loan words. Some newspapers would replace rare kanji with katakana early on. But kanji & hiragana was the norm for non-official stuff.
(People back then might have had a slightly easier time reading all-katakana, though, b/c it was taught first pre WWII and wasn't limited to loan words as it is now.)
Miyazawa wrote his other stuff in kanji and hiragana, so it seems unlikely that he wrote this poem in katakana to make it easier for the local farmers to read.
Rural farmers up north may have had a lower literacy rate than big urban centers in 1930, but compulsory education had been in effect for about 50 years by then. The elementary curriculum set in 1900 included 1200 kanji. Miyazawa had been working up north as a high school teacher. It seems reasonable that he'd expect his work to be published with furigana for any difficult kanji, as was the custom with newspapers and literary journals. His children's stories would likely have the appropriate mix of hiragana and kanji.
He apparently wrote this poem while he while ill shortly before his death. It was written entirely in katakana and found in a notebook in which he'd also written out the Buddhist Lotus Sutra many times. Miyazawa was apparently obsessed with the Lotus Sutra and trying to spread the ideas of the Nichirenism movement (an affiliation which some try to minimize). His other work reflects Buddhist ideas, but this poem is thought by some to be more of simple chant/prayer (I don't know the right word to use.)
His use of katakana might be related to the fact that buddhist scripture in previous centuries used katakana not hiragana. Also, the buddhist incantations had significance beyond their meanings. The act and sound of repetitive recitation was also important. A phonetic syllabary might also allude to that functional aspect of the poem.
Miyazawa was apparently a fan of a few foreign modernist thinkers and artists and influences have been noted. I hadn't heard about an e.e. cummings connection specifically - it'd be interesting to see where that came from. (I wonder if they're trying to connect it to the supposedly humble "i"?) It somehow feels unlikely and contradictory to me that Miyazawa would have experimented with what might be considered a self-indulgent gimmick in a poem such as this, which is a meditation on the ideal self-sacrificing charitable person he strives to be. But I have no idea.
I came across a comment that Miyazawa may have used katakana to convey simplicity. It's a kind of symbolic orthography representation of the values he espoused. Also, the poem itself is not as complex as some of his other stuff. He seems to be seeking the strength not to waver from his aim of actualizing Buddhist principles at a grass roots level by helping to allieviate the suffering of the poor farmers in his community.
Shinichirou, if you do look into this further, please let us know what you find out. Also, if you can remember the name of other poet who used mostly katakana, I'd be interested to know.
Edited: 2012-01-31, 10:03 pm