"The world soul could use more brains."

The aptly named Freeman Dyson--we might almost have called him Freemind Dyson--died this week just short of the age of 100. Dyson once wrote an essay titled “Birds and Frogs,”

in which he described complementary species of mathematicians: “Some mathematicians are birds, others are frogs,” he wrote. “Birds fly high in the air and survey broad vistas of mathematics out to the far horizon. They delight in concepts that unify our thinking and bring together diverse problems from different parts of the landscape. Frogs live in the mud below and see only the flowers that grow nearby. They delight in the details of particular objects, and they solve problems one at a time. I happen to be a frog, but many of my best friends are birds.”

Some might disagree with Dyson’s assessment of himself. “Characteristically clever and self-deprecating,” the author James Gleick replied, when I posted that excerpt on Twitter. “I think he was a bird.”

He elaborated in an email. For a moment, Mr. Gleick said, in the case of quantum electrodynamics, Richard Feynman and Julian Schwinger were the frogs and only Dr. Dyson could see them both: “Schwinger had solved quantum electrodynamics with a difficult formalism that almost no one understood, and Feynman had solved quantum electrodynamics with his powerful diagrams — easy for physicists to use and compute with but still hard to understand — and it was Dyson who saw the thing whole, proving that Feynman’s and Schwinger’s solutions were mathematically equivalent.” He added that Dr. Dyson should have shared their Nobel Prize.