Frank M. Stewart, professor of mathematics, lover of learning, and eager investigator of many aspects of reality, died on Nov. 2 at the age of 93. He had remained active and intellectually curious well into old age, until senile dementia gradually narrowed his horizons and diminished his abilities.

Frank was born on Dec. 27, 1917, in Beirut, Lebanon, where his father was secretary-treasurer of the American University of Beirut. He graduated from Princeton, the family alma mater, in 1939, with highest honors in mathematics, and started working toward his Ph.D. at Harvard immediately thereafter. Exempted from the military on account of poor eyesight, from 1943 to 1945 he was stationed in England as a civilian, working in the Operational Analysis Group associated with the Eighth Air Force.

By then he had met his future wife, Caroline Monks, and their courtship unfolded through the mail. After Frank returned to the U.S. in June of 1945, he was invited to join Caroline and her mother at the Edgartown home of the Chittendens, Caroline’s cousins. She eagerly introduced Frank to the Vineyard, sparking a shared love of the Island that lasted the rest of their lives. Frank returned to graduate school that fall, and the couple were married the following spring, honeymooning at the Kelley House in Edgartown.

After receiving his doctorate in 1947, Frank took a teaching job at Brown University, where he remained for his entire working life. He and Caroline moved to Providence, and in 1951, their only child, William, was born. In 1958 and 1959 and again in 1963 and 1964, the family lived in London, where Frank was a visiting lecturer at Imperial College.

Meanwhile, the family had continued to visit the Vineyard as opportunity allowed. In 1958 they were able to purchase a small house in Lambert’s Cove that they had rented for a few previous summers, located in the woods on Uncle Seth’s Pond. Frank particularly loved fishing on Vineyard Sound in his rowboat, and spending time with old friends and their children when they would come for annual visits.

In 1966, in response to a request from Brown administrators, he spent a semester teaching at Tougaloo, a historically black college in Mississippi with which Brown had established a sister-school relationship not long before. He was profoundly moved by the civil rights struggle that he witnessed there, and he soon became actively involved in the fight for racial justice and equality, returning to Tougaloo for another semester in 1969.

Starting in around 1970, he became increasingly involved in biology, his interest focusing mainly on bacterial population modeling and genetics. He and Caroline spent two more academic years in London, in 1971-1972 and 1978-1979, when he was an honorary research fellow at University College, studying biological problems.

In addition to his academic work, Frank was known for his many interests in a wide range of fields. He was a skilled practitioner of origami, a scholar of Byzantine icon painting, a lover of vocabulary and arcane references who regularly completed the world’s most difficult crossword puzzles, and a devotee of theater and chamber music, to which he brought his characteristic thoughtfulness and erudition. He developed an interest in computers before most people were aware of their existence, and by the early 1970s, he was making computers of his own. He was also a regular squash player until he was over 70.

Frank retired from teaching in 1988. Caroline’s death in 1991 hit him hard, but he but he continued researching, publishing, and attending biology conferences. He also embraced a number of political causes, notably that of the Palestinians, which he supported with no trace of anti-Jewish sentiment, but rather with a passion for justice and with a sympathy for the region’s people formed during his childhood in Beirut. In addition, he was active in the fight to keep Rhode Island from reinstating the death penalty, and was a dedicated member of the Rhode Island ACLU.

Frank’s last great adventure took place in 2005, when he was 87. In that year, his son William arranged for him to attend the 100th anniversary celebrations of the American Community School in Beirut, which he had attended in his childhood. It was his first visit to Lebanon in 70 years, and in a remarkable coincidence, he was invited to stay in the house that had been his childhood home. As the oldest former student in attendance, whose mother had gone to work at the school just four years after it had been founded, he was honored at the culminating festivities, and eagerly sought out for his stories of the old Beirut.

The last few years were hard, on account of advancing dementia, but the end came with remarkable grace. Five days after his hospitalization for pneumonia, he died at Rhode Island Hospice’s inpatient facility, with William at his side.

No memorial is planned, but contributions in his memory may be sent to the Vineyard Conservation Society, P.O. Box 2189 Vineyard Haven, MA 02568.