Robert F. Craggs, Bob to everyone, Yodar Critch to many, the "F" for Francis but don't you dare mention it, died at his home on May 25 after a decadelong bout with Parkinson's disease and its associated form of dementia. He was 85. His wife, Jongin, who'd spent more than half of Bob's years with him, was at his bedside.

Born in South Charleston, Ohio, to Glenden Craggs and Emily Donaldson, Bob was a teacher by trade, a math professor at the University of Illinois for more than 30 years, with a focus on geometric topology and combinatorial group theory.

More than anything, though, he was a lifelong student. Even in the gathering dusk of his compounding diseases, he could be found in his office, scratching out ideas about the famous Poincaré conjecture, the white whale he spent so much of his career chasing. The conjecture was a theorem by that point, having been harpooned by someone else several years ago, but there were still things to learn, Bob believed to the last.

There were always things to learn. He was a serial collector of interests and hobbies. He spoke German and Swiss German, Icelandic, a bit of Norwegian, enough Korean to make conversation with the in-laws, just enough Italian to say the romantic stuff. He wrote well, winning a prize while in grad school at the University of Wisconsin for a Salingerish jewel of a short story. He taught himself to cook, and he came to cook well enough that he was featured in this very newspaper, smiling his warm, gap-toothed smile, for its old "Bachelor in the Kitchen" feature. Bob was so charming in the piece that an anonymous reader felt moved to mail him an apron, which is still in use today. (The accompanying recipe was for veal with almonds served with a spinach-onion pie. The key is to blanch the almonds, boiling them and then pressing them between your fingers until they slip out of their skin.)

One day Bob decided to learn how to work a hand plane and a band saw, and soon enough there were new, finely wrought tables all around the house and a loom as well. And one day, having spent so many weekends driving his son, Tommy, to chess tournaments all over the country, he decided to try his hand at tournament chess, too. He didn't win much, but winning wasn't the point. The point was the seeking itself.

Bob is missed dearly by kin and colleague alike: by Jongin and Tommy and Tommy's partner, Kelsey; by his granddaughter, Nora; by his nephews and nieces, Thad, Marla, Connie, Paul, Youngmoo, Charlene, Tony, and Cyndy, and their children, Zeke, Turner, Alex, Ryan, Connor, and Katie; by his fellow mathematicians and especially by his former PhD students. Some 35 years ago, several students started a seminar series affectionately called the "Disciples of Yodar Seminars," using the nickname he'd given himself. (Jongin liked to say he had such a big heart he needed two names.) Among those students was Tony Bedenikovic, now a professor at Bradley, who described Bob as having run "at full speed toward the mathematical challenges" of the day, "his knowledge of the known always joined by a unique, wildly creative perspective for how to approach the unknown." May he find yet more things to learn in this last unknown.

A memorial service will be held at 11 a.m. on Saturday, June 17, at the Unitarian Universalist Church of Urbana-Champaign, corner of West Green and Birch in Urbana. Memorial contributions may be made to Carle Hospice (4116 Fieldstone Rd, Champaign, IL 61822 or carle.org/giving), the minister's discretionary fund at the Unitarian Universalist Church of Urbana-Champaign (309 West Green Street, Urbana, IL 61801 or uucuc.org), or the Entertainment Community Fund (729 Seventh Ave, 10th Floor, New York, NY 10019 or entertainmentcommunity.org) in solidarity with the Writers Guild of America's strike.