When he returned, he was suspended from his job, his reputation was in tatters, and his loyalty was in question. Later, he was cited for contempt of Congress.
All for taking the Fifth Amendment.
Back at Temple, he quickly became the man in the middle.
On one side were the conservatives, the state politicians - many of them rabidly anti-communist - the editorial writers and university officials, who feared the school would lose funds if Dr. Dunham to kept his position.
On the other side were Dr. Dunham's defenders - Temple alumni, students, teachers and labor unionists who circulated petitions, held rallies, and gave him awards for courage.
Coincidentally, while this was happening to Dr. Dunham, the president of Temple University, Robert L. Johnson, was being groomed to head the International Information Service, the parent body of the Voice of America and one of the agencies that McCarthy and his followers said was riddled with Reds.
In those days, no one - and especially the head of such an agency - could afford to be considered soft on communism.
Already, the state required the loyalty oaths of teachers. At Temple, that meant that each chairperson had to certify that there were no "subversives" in his or her department - something that Dr. Dunham had already done.
But once the finger of suspicion was pointed at him, nothing could save his name or his job.
It didn't matter that the professor, a Princeton University graduate with a doctorate in philosophy, had taught at Temple for 16 years, with never the shadow of an accusation that he was trying to brainwash his students.
"No one ever accused him of using the classroom as a pulpit for his political beliefs," said his grandson, Robert Dunham. "And no one ever disputed that he was a well-loved professor."
His Temple ties were extensive. His father had taught there for 30 years and had been dean of the College of Liberal Arts. Both his son, Clarke, and daughter-in-law were Temple grads, and his wife had earned her master of fine arts degree at Temple's Tyler School.
But from 1938 until 1945, Dr. Dunham was a member of the American Communist Party. And he admitted that his thought had been deeply influenced by Karl Marx.
He had been, he told an interviewer, "part of the great leftward swing in the 1930s - and any intellectual worth a damn was a part of that."
They paid dearly for that "leftward swing" in the McCarthy era, a time of loyalty oaths and the posing of the question: "Are you now, or have you ever been, a member of the Communist Party?"
Dr. Dunham was no subversive, but nothing he did could convince the school's Loyalty Oath Committee or the board of trustees of that.
The board accused him of "intellectual arrogance" in his appearance before HUAC and said he took the Fifth "to evade his duty. " It fired him and barred him from campus.
The action was heartily endorsed by the city's editorial writers.
The Inquirer weighed in with: "Dunham himself made it inevitable - not only by his refusal to answer the most elementary questions of the HUAC, but by his breast-beating arrogance which would be amusing in a know-it-all sophomore, but which is definitely unfunny in a 47-year-old professor of philosophy."
Throughout the ordeal, Dr. Dunham claimed the moral high ground.
"No man was ever dismissed for reason that did him greater honor," he said at the time.
By firing him, the trustees had liberated him, he said. "But they have put themselves in chains. They have surrendered to the first political adventurer who passed by."
He said he refused to answer HUAC's questions because "I don't want to become a party to a medieval inquisition." The probers didn't use thumbscrews or other torture machines, he said. They used contempt citations and perjury indictments to gain their ends.
The real victims, he said, were the students "who, under coerced instruction, will lose large portions of their cultural heritage. Without the right to hear, to speak and to think, learning will become a mere rote memory.
"I think, therefore, that teachers must defend the whole tradition - if necessary with their jobs. For if we begin concealing the knowledge we have, we shall no longer be teachers, we shall be hacks."
Dr. Dunham returned to Temple following his ostracism for the first time in 1977 when he was guest speaker at the annual induction of Phi Beta Kappa. His experience lent his speech on moral courage an uncharacteristic immediacy.
Thinkers, he said, should be prepared to encounter the enemies of truth using "defamation, excommunication, imprisonment and death" as their weapons. "Accept your own vulnerability. Prepare to be hurt," he said.
What he had feared most, he said later, was social isolation. But it never happened. "Neighbors would talk over the hedge, and they would come by for tea. In this kind of struggle," he said, "you meet the best people."
After his ouster, Elizabeth Flowers, a philosophy professor at the University of Pennsylvania was asked to take over his courses. She refused. ''It was a terrible thing they did at Temple," she said. "We were all disappointed that the faculty senate there wasn't more effective."
Barred from the campus, he was deprived even of the use of the library. He was welcome to do his research at Penn's library and welcome to use half of Flowers' office.
Flowers said the strongest association she had involving Dr. Dunham was not with Marxism or ethics, but with his popularizing a baseball story in which three umpires compare calls.
" 'I calls 'em as I sees 'em,' says the first. 'I calls 'em as they are,' says the second. 'Don't be silly,' says the third. 'They are as I calls 'em.' ''
This was baseball serving philosophy. The story was Dr. Dunham's shorthand for describing theories of knowledge.
Dr. Dunham held a variety of part-time teaching positions during the intervening decades - at Beaver College, the University of Pennsylvania and Montgomery County Community College. He also wrote several more books, six in all.
In 1955, a federal District Court in Washington overturned Dr. Dunham's contempt-of-Congress conviction, and, a year later, the American Association of University Professors censured Temple University for firing Dr. Dunham without due process.
Temple attempted to make amends in 1981 by appointing Dr. Dunham emeritus professor of philosophy. That enabled him to collect his pension, which had been denied him after he was fired. But he never taught at the school again.
At Dr. Dunham's reinstatement, Temple president Marvin Wachman acknowledged that the ceremony "removes a painful vestige of McCarthyism, that sad and bitter period in our national history."
"I'm delighted, of course," Dr. Dunham said at the time. "We ought never to have been parted, but that was the kind of thing that happened 28 years ago. I'm glad to be back."
In addition to his son, Clarke, he is survived by his wife, Alice Clarke Dunham, who was born on the same day and in the same town as her husband, and four grandchildren.
A memorial service will be held at a later date.