The physicist John Trump, in a high-voltage research lab at M.I.T. He was the younger brother of Donald Trump’s father, Fred. Photograph by Alfred Eisenstaedt / The LIFE Picture Collection / Getty

In September, 1936, a reporter for the Associated Press watched the unveiling of a new kind of X-ray machine, said to be able to generate a million volts of power. The scientist operating the device was John G. Trump, a professor of engineering at the Massachusetts Institute of Technology. Trump was working the controls and explaining how high-speed electrons ran along a porcelain tube to a “water-cooled gold target,” when suddenly “two of the high-voltage sparks hit him squarely on the nose.” And yet, according to the A.P. account, the direct strike caused him only “slight discomfort.” Professor Trump told the reporter, “That’s an advantage of this machine. It’s completely grounded and those sparks can’t kill you.”

If only the same could be said of the Presidential campaign run by Professor Trump’s nephew, Donald J. Trump. He is still uncomfortably close to victory, which is why there have been, lately, more serious attempts to figure out what he might do if, say, he had access to nuclear weapons. In his answers, he seldom sounds as ungrounded as when he invokes Professor Trump, the younger brother of his father, Fred. “My uncle used to tell me about nuclear before nuclear was nuclear,” Trump said in one interview, “before nuclear” referring, perhaps, to the development of hydrogen bombs, rather than basic atomic bombs (which occurred when Donald was about six years old), or perhaps just to that netherworld where things wait until Trump judges them to be fashionable or flashy enough to exist. He mentions his uncle so often, and in such extravagant terms—“brilliant,” “one of the top, top professors at M.I.T.”—that it seems worth asking what the professor and his arcane knowledge mean to him. There are two different sets of answers, which might be put into the category of foreign and domestic.

But first, given Trump’s tendency to wrap things in porcelain and gold and shoot sparks through them, it’s worth noting that John Trump really does seem to have been a brilliant scientist. He was at M.I.T. for decades, and the X-ray machines he helped design “provided additional years of life to cancer patients throughout the world,” as the Times put it in his obituary, in 1985. Trump was involved in radar research for the Allies in the Second World War, and in 1943 the F.B.I. had enough faith in his technical ability and his discretion to call him in when Nikola Tesla died in his room at the New Yorker Hotel, in Manhattan, raising the question of whether enemy agents might have had a chance to learn some of his secrets before the body was found. (One fear was that Tesla was working on a “death ray.”) As Margaret Cheney and Robert Uth recount in “Tesla, Master of Lightning,” Professor Trump examined Tesla’s papers and equipment, and, in a written report, told the F.B.I. not to worry: Tesla’s “thoughts and efforts during at least the past 15 years were primarily of a speculative, philosophical, and somewhat promotional character,” but “did not include new, sound, workable principles or methods for realizing such results.” Professor Trump may have neglected to make that sort of distinction clear to his nephew.

What is strange is that Donald Trump couples tales of how he received early, secret word from his uncle that nuclear weapons were dangerous and getting more so—“He would tell me, ‘There are things that are happening that could be potentially so bad for the world in terms of weaponry,” he told the Boston Globe—with a casual indifference about proliferation. In recent interviews, Trump has said that if countries like Japan and South Korea didn’t want to pay America more for military protection, they should go and build their own nuclear weapons. When, in one seesawing exchange, Anderson Cooper asked if this meant he was for proliferation, Trump first disagreed, citing—naturally—the professor. “I hate nuclear more than any. My uncle was a professor was at M.I.T., used to tell me about nuclear,” Trump said. But then he added, “Can I be honest with you? It’s going to happen, anyway. It’s going to happen anyway. It’s only a question of time . . . Now, wouldn’t you rather in a certain sense have Japan have nuclear weapons when North Korea has nuclear weapons?” (Actually, no.)

It’s true that nuclear weapons are not that hard for a determined country to acquire, which is why the best counter-proliferation tool is diplomacy—that is, deal-making, which Trump prides himself on and yet, in this case, tosses aside. Last week, President Obama attended an international summit on nuclear weapons, in Washington, and said in a press conference that the representatives of other countries had told him they were worried about Trump, who, Obama said, “doesn’t know much about foreign policy or nuclear policy or the Korean Peninsula or the world generally.”

It gets stranger still when Trump invokes the bomb as a way to dismiss talk of climate change: “The only global warming I’m worried about is nuclear global warming.” Was he thinking of the nuclear winter, but got it backward? Or of the heat generated when bombs, which his uncle told him would be nuclear even before there was nuclear, detonate? It may be, as is so often the case, that looking for the logic in Trump’s comments is a pointless exercise. But they might provide an outline, at least, of a world view. When Trump told the Times that his uncle “would tell me many years ago about the power of weapons someday, that the destructive force of these weapons would be so massive, that it’s going to be a scary world,” maybe his point was that the world is a scary place, and thus well-suited for a politician like him, who traffics in fear.

Then there is the domestic side. Trump brings up his Uncle John on subjects that have nothing to do with technology, such as when the Washington Post asked him about his tendency to use crude language and insult people. Trump said that that wouldn’t continue when he was President—and why not? “My uncle, I would say my uncle was one of the brilliant people. He was at M.I.T. for thirty-five years. As a great scientist and engineer, actually more than anything else, Dr. John Trump—a great guy.” That was followed not by a quote from his uncle about, say, the importance of treating people decently, but by the simple statement: “I’m an intelligent person.” This is the professor’s other role in the Trump rhetorical universe: as a sort of eugenic guarantor of intelligence and breeding.

It is a theme that comes up often. “I had a father who was successful,” Trump told CNN, in 2010. “And, you know, I have a certain gene. I’m a gene believer. Hey, when you connect two race horses, you usually end up with a fast horse.” In South Carolina, earlier this year, he noted, “Dr. John Trump at M.I.T.; good genes, very good genes, O.K., very smart, the Wharton School of Finance, very good, very smart.” (Donald Trump was at Wharton as an undergraduate, after transferring from Fordham.) To the Boston Globe: “My father’s brother was a brilliant man . . . We have very good genetics.” And then on NBC, after telling Lester Holt that his uncle was a professor at M.I.T.: “I mean it’s a good gene pool right there”—he pointed to his head—“I have to do what I have to do.”

Looking at Trump’s ideological assemblage, one can see certain common connectors—fatalism, fear, and a social-Darwinist’s contempt for those who don’t do quite as well as he and his family have. Being born rich isn’t luck; it’s something to congratulate oneself on when one looks in the mirror. The opposite is true of the “losers.” It’s part of what can make Trump feel both like a doomsayer and a smug child. In his rallies, he has taken to giving dramatic readings of the lyrics of a song, by Al Wilson, called “The Snake,” which he presents as a parable about the dangers of immigration: a woman saw a beautiful snake at the side of the road, almost dead from the cold. She took it home, warmed it up, saved its life, and “clutched it to her bosom”—Trump always emphasizes that phrase—whereupon it bit her. As she died from the venom, she asked why. “You knew damn well I was a snake!” Trump shouts. The world is scary; people don’t change. All a Trump can do is ride down an escalator to the lobby in Trump Tower, past the gold fittings and the waterfall, and say that he’s running for President. Then come the sparks.