Computational analysis reveals how a samurai classic carried Japanese moral values to the West

In 1899, the Japanese educator Inazo Nitobe published a book in English called Bushido: The Soul of Japan, an attempt to explain the ethics of the samurai class to Western readers at a time when few outside Japan understood how the country transmitted moral instruction. Nitobe, who was born into a samurai family and later converted to Christianity, wrote the book after a Belgian legal scholar asked him how Japan taught morality to its children without religious instruction in schools. Nitobe came to realize that the answer lay in the samurai code he had grown up with, and he set it down for foreign audiences through seven virtues: rectitude, courage, benevolence, politeness, veracity, honor and loyalty.

The book became an international bestseller, and U.S. President Theodore Roosevelt counted it among his favorite reads. More than a century later, two psychologists at Nagoya University in Japan, Ryota Takano and Minoru Karasawa, have revisited the classic with a tool Nitobe could never have imagined: computational language analysis. In a study published in PNAS Nexus, the researchers examined how the moral values in Bushido are structured and expressed, and how the book compares with hundreds of other English-language moral and cultural texts.

Their work addresses a long-standing gap in psychology, which has relied heavily on Western populations, by asking how values originating elsewhere are understood when they cross linguistic and cultural borders. The analytical backbone of the study is a widely used psychology framework that groups moral values into six basic concerns: care, equality, proportionality, loyalty to one's group, respect for authority and purity. Proportionality refers to rewards that match a person's contribution.

Psychologists typically measure these concerns with questionnaires such as the Moral Foundations Questionnaire, in which people rate how much they agree with statements like "Caring for people who have suffered is an important virtue" or "I feel that most traditions serve a valuable function in keeping society orderly." Applying such an instrument to a book required a translation step from human ratings to machine-readable meaning. That step was achieved through a method called contextualized construct representation, or CCR. A language model converted every sentence in each book, along with each of the 36 questionnaire statements, into numerical vectors representing their meaning.

The team then measured how closely each sentence matched each statement in semantic space, with a higher score indicating that the text expressed that moral concern more clearly. To ensure the results did not hinge on one particular model, the researchers repeated the scoring with three other language models and found that the scores closely matched across all of them. "The method is very simple.

It calculates the similarity between sentences," said Takano, a lecturer at Nagoya University's Graduate School of Informatics and the study's first author. "On one side is a sentence from Bushido, and on the other is a statement from an established questionnaire." For comparison, the researchers applied the same procedure to hundreds of other English-language texts drawn from the free online library Project Gutenberg, including works on Christianity, the Bible and Japanese culture. This gave them a broad baseline against which the moral profile of Nitobe's book could be judged.

Compared with the other texts, Bushido displayed a distinctive pattern across the six moral concerns. It expressed all six slightly more clearly than the average of the comparison texts, with the clearest difference observed in respect for authority. Takano noted that this pattern is consistent with samurai culture, which placed great importance on social hierarchy.

The researchers also analyzed the seven chapters of Bushido, each of which describes one of the virtues. Across those chapters, certain moral concerns tended to score high or low together, and the team used this correlational structure to sort the six concerns into two broad groups. One group contained respect for authority, equality, proportionality and purity; the other contained care and loyalty to one's group.

Honor emerged as the only virtue strongly tied to both groups, making it the connective tissue of the book's moral architecture and the virtue linked to more of the six concerns than any other. Takano cautions that the honor described in the book is not identical to its Western counterpart. "Meiyo is not the same as honor in the Western sense, which is more related to self-enhancement and prestige," he said.

"Meiyo is based on patience. Samurai had to control their emotions and suppress negative feelings." He also draws a boundary around what the study can claim: "Our study describes how an English-language book presented Japanese ideals to Western readers. It does not reconstruct the ethics of historical samurai." In other words, the analysis measures the values as Nitobe packaged them for a foreign audience, not the lived code of the warrior class itself.

Beyond the internal structure of the book, the study asked why Bushido resonated abroad. The researchers compared it with 30 other English-language books about Japanese culture and measured how widely each had spread in the West, counting English editions, translations into French, German, Spanish, Italian and Dutch, and citations on Google Scholar. Bushido ranked second among these books, just behind The Book of Tea.

Crucially, the closer a book's mix of moral concerns matched Bushido's profile, the more widely it tended to be published, translated and cited. Books about Japan that echoed its moral signature traveled further. Coauthor Karasawa, a designated professor at the Graduate School of Informatics, sees the result as evidence of a successful act of cultural translation.

"Bushido presented Japanese values in terms Western readers could relate to, while keeping its own distinct character," he said. "Now, with advances in natural language processing, we can measure the values in hundreds of texts at once. That lets us compare moral traditions across cultures in ways that traditional reading cannot easily do." The study suggests that Japanese values may have reached Western readers partly because of how Nitobe expressed them, not only because of what they were.

The researchers now aim to apply the method to classics, religious texts and literature from other cultures to learn how cultural values are shared and accepted across countries and regions.

Subject of Research: Computational analysis of moral values in the 1899 book Bushido: The Soul of Japan and their reception in the West

Article Title: How a samurai classic shared Japanese values with the West

Article References: How a samurai classic shared Japanese values with the West. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Bushido, Inazo Nitobe, moral foundations, computational text analysis, natural language processing, samurai ethics, honor, cultural psychology, Nagoya University, PNAS Nexus, cross-cultural values, Project Gutenberg