A Mathematician Who Spoke of the Human SoulThe name Oka Kiyoshi may not immediately bring a face to mind for many people today. Yet in the history of 20th-century mathematics, his achievements were truly remarkable on a global scale. He was the man who solved, almost entirely on his own, a series of extraordinarily difficult problems in the theory of functions of several complex variables — a field that had barely been touched at the time.As Oka grew older, however, he found himself drawn less to mathematics itself and more to the questions of what it means to be human and what it means to be Japanese. The idea he returned to again and again was that emotional sensitivity — what he called jōcho in Japanese — lies at the very center of human existence. "Emotional sensitivity can only grow in slowness" is the phrase that captures the essence of that belief in a single sentence.In an age that prizes speed and places efficiency above all else, these words may sound almost provocative. But when we take the time to read carefully what Oka was trying to say, we discover that it is neither nostalgia nor anachronism. It is a profound insight that touches something fundamental about what it means to be human.The Life of Oka Kiyoshi and the Roots of His ThoughtOka Kiyoshi was born in 1901 and died in 1978. He studied mathematics at Kyoto Imperial University, spent time in France as a researcher, and upon returning to Japan taught at Nara Women's University. His career, however, was far from smooth.He devoted more than twenty years to tackling the three great unsolved problems of the theory of functions of several complex variables — the Hartogs inverse problem, the Levi problem, and the first cohomology problem. Life was financially difficult, his family endured considerable hardship, and there were periods when he was pushed to the edge mentally and emotionally. Even so, he never abandoned his research. It was during these long years of solitude that Oka developed his distinctive thinking about the relationship between mathematics and human existence.In the 1960s, he began to express his ideas less through technical mathematical writing and more through essays and conversations. His dialogue with the literary critic Kobayashi Hideo, published as Ningen no Kensetsu — The Construction of the Human Being — in 1965, is perhaps his most celebrated work outside of mathematics. The two men ranged freely across mathematics, art, and the formation of the human character, and the book continues to find new readers to this day.Why did a man who lived in the supremely logical world of mathematics come to place such emphasis on emotional sensitivity? The answer lies in his own experience as a creative mathematician. Before any proof was constructed, there was always a feeling — a sense that something was beautiful, that a certain direction was right. That feeling was what he meant by emotional sensitivity, and without it, he believed, a mathematician could not take a single step forward. Logic, he insisted, comes after. What moves first is feeling. Coming from a mathematician of his stature, this claim carries uncommon weight.What Does Slowness Actually MeanIf we take the phrase "emotional sensitivity can only grow in slowness" at face value, it might sound as though the message is simply that we should spend more time on things. But what Oka meant by slowness was something considerably richer than that.For Oka, slowness meant the kind of time and space in which something can grow from within, unhurried by demands from the outside. When we are rushed, we do only surface-level processing. We receive information, react to it, and move on to the next thing. There is no room in that sequence for the act of truly feeling. And because emotional sensitivity grows through feeling, it cannot grow where there is no time to feel.A simple image may make this clearer. Imagine a child who discovers an insect. A busy adult says, "Come on, we have to go," and walks past. But a child with time will crouch down and stare at it, touch it, follow where it goes. Through that accumulation of experience, a sensitivity to living things and a sense of intimacy with the natural world quietly develops. This is precisely the kind of emotional sensitivity that Oka believed could only grow in slowness.Oka was particularly concerned about this in the context of children's education. He warned that modern schooling, in its rush to fill children with knowledge and prioritize speed above all else, was cutting away the very sensitivity that children naturally possess. No matter how quickly you can fill a child with facts, if the emotional sensitivity needed to make use of those facts has not grown, the child will reach adulthood without any inner axis to stand on.Knowledge, he said, is a tool. What determines how a tool is used is something that lives inside the person holding it. Oka called that something emotional sensitivity, and he believed it was the foundation of all genuine human development. To cultivate it, slowness was not merely helpful — it was essential.Is This a Uniquely Japanese Sensibility, or a Universal QuestionOka's thinking about emotional sensitivity is deeply entwined with Japanese cultural tradition. He frequently drew on concepts such as mono no aware — the bittersweet awareness of transience — as well as wabi, sabi, and yūgen, those distinctly Japanese aesthetic values that resist easy translation. All of these sensibilities were nurtured in a culture that did not hurry, that honored quiet, and that preserved space for what is left unsaid.This naturally raises a question. Is Oka's thinking something that only makes sense within the specific cultural context of Japan?The answer is no. The essential question he was asking — whether the relentless pursuit of speed and efficiency causes us to lose something that is irreplaceable to human life — began to surface independently in many parts of the world during the latter half of the 20th century and into the 21st.The Slow Food movement, which began in Italy in the late 1980s as a response to the spread of fast food culture, was animated by the desire to recover the pleasures of eating, the vitality of regional food traditions, and the warmth of connection between people. This was precisely an effort to protect what can only grow in slowness. In 1999, the journalist Carl Honoré developed what he called the Slow Movement, arguing for the value of living at a more human pace in a world that had come to treat speed as the natural condition of things. His book In Praise of Slow was translated into more than thirty languages.In philosophy, the French thinker Paul Virilio introduced the concept of dromology — the study of speed — and argued that as society accelerates, human perception and culture progressively deteriorate. In education, the concept of deep learning has attracted growing attention, with a shift away from surface-level acquisition of knowledge toward approaches that emphasize the slow processes of thinking, feeling, and genuine understanding. This, too, shares its roots with what Oka was pointing toward.In other words, Oka's thought emerged from the particular soil of Japanese culture, yet it was simultaneously reaching toward something universally human. Oka himself was aware of this. He spoke of Japan's culture of emotional sensitivity as something to be proud of in the world, while also suggesting that it was not exclusively Japanese — rather, Japan had been unusually good at preserving something deeply human that modernity, industrialization, and acceleration had been stripping away everywhere.Surprising Parallels in World ThoughtStrikingly similar ideas to Oka's can be found in many different places across the world.The American writer and philosopher Henry David Thoreau built a small cabin beside Walden Pond in Massachusetts in 1845 and lived there for two years, recording the experience in Walden, published in 1854. What Thoreau sought was also an inner richness that could only be cultivated by not hurrying, by placing silence and open space at the center of one's days in nature. Thoreau and Oka never influenced one another directly, but the questions they were asking overlap in remarkable ways.The ancient Chinese philosopher Laozi left these words: "In pursuit of learning, every day something is gained. In pursuit of the Way, every day something is dropped." Knowledge may be accumulated by addition, but walking the path of being fully human requires, on the contrary, a process of letting go. The wariness toward endlessly piling on more information and more stimulation is something Laozi and Oka shared across the centuries.The concept of samatha — stillness — in Indian philosophy also offers an interesting resonance. In meditative practice, deliberately bringing the mind to a state of stillness and non-movement is understood to open the way to deeper insight. The idea that an inner space is opened by stopping the rush and simply being present echoes Oka's understanding of slowness in a compelling way.There is also a fascinating anecdote worth sharing here. In his later years, Oka frequently told young researchers that the solutions to mathematical problems never came when he was sitting at his desk trying to solve them. They came during walks, or in moments of aimless reverie. This was not merely an interesting personal observation. It turns out to be deeply connected to what cognitive science now calls the default mode network — the neural circuitry of the brain that becomes most active precisely when a person is not focusing on anything in particular, when the mind is drifting and apparently idle.Research in neuroscience has shown that this is the state in which creative leaps and genuine insight are most likely to emerge. What Oka described from his own lived experience, modern science has since confirmed. Slowness, open space, and unhurried time are not merely conditions for the growth of emotional sensitivity — they are indispensable to creative intellectual life as well.Reading Oka as a Question for Our Own TimeOka made his observations about emotional sensitivity and slowness in the 1960s and 1970s, when Japan was in the midst of its period of rapid economic growth and the entire society was racing toward speed and efficiency. His words were, among other things, a serious warning directed at that moment in history.More than half a century has passed since then, and the pace of society has accelerated far beyond what Oka witnessed. Information arrives in an instant through smartphones. Social media demands a constant stream of reactions. Artificial intelligence produces answers faster than human thought. Children today are born into an environment of high-speed information from their very first days, and the time needed to slowly feel something — to let it sink in — can only be preserved through conscious effort.Perhaps Oka's words deserve to be asked more deeply now than ever before. What do we do with the time that efficiency has freed up for us? Are we using it to chase yet more speed? With all the time we have saved, are we feeling more, or less?Oka called emotional sensitivity the center of the human being. If that center is unstable, then no matter how capable a person may be, those capabilities will not naturally move toward what makes human life genuinely worth living. As artificial intelligence develops with extraordinary speed, the question of what grounds human beings in their humanity becomes ever more urgent. As a perspective from which to reexamine that question, Oka's thought has a relevance today that may be greater than it has ever been.Slowness is not laziness. Slowness is a condition for richness. Time in which something is felt deeply, and allowed to work its way into the interior of a person. Out of that quiet accumulation, Oka teaches us, the emotional sensitivity that makes us human slowly and surely grows.ReferencesOka Kiyoshi. Shunshō Jūwa (Ten Talks on a Spring Evening). Kōbunsha Bunko, 2006. Oka Kiyoshi and Kobayashi Hideo. Ningen no Kensetsu (The Construction of the Human Being). Shinchō Bunko, 1965. Oka Kiyoshi. Sūgaku suru Jinsei (A Life of Doing Mathematics). Shinchō Bunko, 2013. Carl Honoré. In Praise of Slow. Orion Books, 2004. Henry David Thoreau. Walden; or, Life in the Woods. Ticknor and Fields, 1854. Laozi. Tao Te Ching. Various annotated editions. Paul Virilio. Speed and Politics. Semiotext(e), 1986. Buckner, R. L., Andrews-Hanna, J. R., and Schacter, D. L. "The Brain's Default Network." Annals of the New York Academy of Sciences, 2008. Nakamura Yūjirō. Kansei no Kakusei (The Awakening of Sensibility). 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