Karl Jaspers, the psychiatrist-philosopher who became the moral conscience of a defeated German nation, was described by his most famous pupil, Hannah Arendt, as knowing all too well that political questions were too serious to be left to politicians. Jaspers believed that politics should concern everyone—as should philosophy. With writings such as Vom Ursprung und Ziel der Geschichte (1949; Origin and Goal of History), he explored the ramifications of what we now call the global village; with Die Schuldfrage (1946; The Question of German Guilt) and Die Atombombe und die Zukunft des Menschen (1958; The Atom Bomb and the Future of Man), he addressed the pressing issues of his time.

Politics and philosophy do govern most of what the author chooses to include in this curious hybrid of a biography, which strives to be a chronology of relationships and events, punctuated by the development of a philosophy. It turns out to be a little of both the life and the work, but not enough of either to be fully satisfying. Kirkbright, a British scholar, describes how the book began after she met Hans Saner, who had been Jaspers's assistant at Basel University and became his first biographer and editor of his literary estate. What started as a research project in Germany during a sabbatical semester was transformed into a "vocation" when Kirkbright relocated to "the vicinity of the archives" in Marbach am Neckar to dedicate herself to researching Jaspers's life and work. Saner gave her access to the thousands of letters in the Jaspers archives in Marbach am Neckar, many of them exchanged between Jaspers and his parents, from his boyhood in the 1880s to shortly before his 1969 death.

Kirkbright relies on these letters as her primary illustration of the development of Jaspers's philosophy, quoting them liberally but without explanation or commentary. Rather than bolster them with her own interpretations and insights, she expects the letters to serve as definitive proof of contentions that are as difficult to discern for the Jaspers scholar as they are for the general reader.

One wishes Kirkbright had approached the letters with a more critical eye rather than privileging them, as she has done, as the supreme vehicle for understanding Jaspers's intellectual life. She uses them to best effect in her discussions of how Jaspers's father influenced his eldest son; she is weakest in the long chapter dedicated to Jaspers's relationship with his younger brother, Enno, whose dissipated life of one failure after another ended in suicide.

The technique of equating Jaspers's life and work so unequivocally with his letters might have worked better had Kirkbright delivered her infrequent assertions with authority. Too often, she is timid and unfocused, and she writes in such a haze of conditionals ("perhaps," "it may have been," "might have seemed") that it is difficult to trust her judgments. Her prose is turgid and elliptical, but she still tantalizes, even as she frustrates by telling the tale of an appealing subject in a dull book.

From the letters, Jaspers (born in 1883 in the north German town of Oldenburg) does appear to have had a supremely happy childhood and young adulthood. His rapport with his parents was one of lifelong affection and mutual respect of the sort not often found in lives that merit biographies. Jaspers was the eldest son of a prosperous businessman of liberal leanings who held various civic offices, among them chairman of the Oldenburg town council and representative to the regional parliament. Jaspers's father was skeptical of political authority, several times declining to become a member of Bismarck's national parliament, the Reichstag. This skepticism extended to organized religion as well. Though Karl Jaspers was confirmed in the Protestant church, he was far more willing to accept the new ideas that his father espoused. Arendt described this quality as not actually breaking "with tradition but with the authority of tradition," in what became for Jaspers a continuous quest for "universal relativity."

Kirkbright writes comfortably in the book's early chapters of how Jaspers's education was both classical and humanist, and how his study of the Greek and Roman languages and civilizations "strengthen[ed] his sense of belonging to a cultural state of learned libertarians." By the time he was in secondary school, his father had become a bank official and managed his family as shrewdly as his business, both of which flourished financially. This was fortunate for Jaspers, whose lungs had been imperiled since childhood. His condition was formally diagnosed as "bronchiectasis," a chronic enlargement of the bronchial tubes, in 1901, when he was a law student at the University of Freiburg. His naturally intellectual bent matured during periodic rest cures, and during one in the Swiss resort of Sils Maria, he decided that practicing law required better health and more energy than he was ever likely to have. In 1902, then, he switched to medicine, and in 1908 he qualified as a doctor. From the beginning of his medical studies, Jaspers's curiosity about the world at large was evident, as Kirkbright demonstrates through a 1902 photo showing Jaspers between an Italian physiologist and a German art historian.

Jaspers was at Heidelberg University when a fellow medical student, Ernst Mayer, broached the invisible social divide separating Jews from Christians to introduce Jaspers to his sister, Gertrud. The self-described "North German block of ice" said afterward that the couple's "fate was decided within an hour" of their first meeting. Seeking to explain what had hit him, Jaspers wrote, "it was as if lightning had struck, and something had been decided in one moment for all time." Kirkbright interprets this as "not so much romantic as based on the idea of a collision between time and eternity"—a fairly mundane gloss, but no matter. Even philosophers fall in love, and the marriage was long and happy.

It's more difficult to accept some of Kirkbright's other judgments so easily, particularly when she writes of the people who were influential in Jaspers's maturity. Kirkbright calls Max Weber one of his "most influential mentors," and most scholars would agree. But here again, her assertions lack both detail and authority. Her timidity is most evident when she writes of how, after Weber's death, Jaspers seemed to ignore "a potential discrepancy between Weber's public and private life." No women are named in the text, and the endnotes refer only obliquely to other writings, leaving the frustrated reader to seek additional sources for clarification. This example is representative of Kirkbright's treatment of both other persons (Martin Heidegger in particular) and other topics (particularly Jaspers's interest in van Gogh).

Once she comes to the ascendance of the Nazis, when Jaspers's marriage to a German Jew forced his withdrawal from public life and the teaching profession, Kirkbright writes with more authority. This "inner emigration" was necessitated by the fact that "reliable Nazis" could no longer protect the once-privileged mixed marriage. Gertrud was forced into hiding on three occasions before the couple decided to spend the rest of the war hiding in plain sight, living their lives sequestered in their Heidelberg apartment. Here again, Kirkbright tantalizes with descriptions of how the two worked together and what each contributed emotionally to their marriage. It certainly isn't necessary to turn every wife of a gifted man into the true power behind his creative throne, but Gertrud Jaspers's role in her husband's life deserves more scrutiny than Kirkbright provides with the occasional vague comment about Gertrud making a contribution to a specific work.

Jaspers became best known in the postwar years, when he moved to Switzerland to take on a professorship at Basel University. Starting with his 1947 study Vom Europäischen Geist (The European Spirit) and continuing with his two-volume Die großen Philosophen (1957; The Great Philosophers), Jaspers became known as a philosopher who was truly engaged with the problems of the modern world. Accolades began to pour in, among them the Erasmus Prize, an honorary doctorate from the Sorbonne, and the German Peace Prize and the Order of Merit, both from the then­Federal Republic of Germany.

Kirkbright dutifully plods through the details of Jaspers's postwar years without much grace. She tries to create a unified theme with which to conclude his life in her final chapter, touching upon Arendt, Weber, and Heidegger before she settles in to tell a family story. In her penultimate sentence, she tells of how Jaspers's father gave Gertrud a writing desk that had been in the family for several centuries as if the event had just recently happened—and even though the father had been long dead—leaving the puzzled reader to turn to the notes to learn that Jaspers's father gave the gift welcoming Gertrud into the family in 1912. Kirkbright's next sentence, the last in the book, begins with the date of Gertrud's ninetieth birthday, February 26, 1969, when she sent a telegram to Arendt saying Jaspers had just died. Kirkbright might have offered a few observations to soften such an abrupt ending—perhaps a line or two from his memorial service, where Arendt spoke movingly of the philosopher's personal integrity and the "fusion of freedom, reason, and communication" that he exemplified. Kirkbright strives valiantly throughout her book to show these qualities. One wishes she had been more successful at the task.

Deirdre Bair is the author of Jung: A Biography (Little, Brown, 2003)