For a man who is seen as the devil incarnated by most white Rhodesians and even some black, Robert Mugabe hardly seems to fit the image.

The guerrilla leaders who was overwhelmingly elected today to be the first prime minister of an independent Zimbabwe comes across mostly as a somewhat diffident, scholarly professor, earnestly trying to get his students to understand a point.

He deals well with small groups and with the press but lacks the ability of many black African politicians to enthrall the huge political rallies so common here. At times, some of his listeners feel he talks over their heads.

One long-time Mugabe watcher explains it by saying, "He's too much of an intellect to have charisma."

Mugabe also stands out among his country's politicians for his reputation of holding to a position and not shifting with the various political winds despite some evidence that, once in power, he may be forced into changes in order to cope with a tense government situation.

He admits that this firmness probably is linked to the fear with which he is held in some quarters. "If I determine the stand I am taking is the correct one, a principled stand, then I stick to it," he told an interviewer last year.

With his trace of a goatee, horned-rim glasses and natty suits often from London's stylish West End, he hardly looks like a man who spent 10 years in Rhodesian prisons for his opposition to the white government of former prime minister Ian Smith.

How Mugabe, who neither drinks nor smokes, used the decade, however, gives an inkling of the man's preserverence: he earned three advanced degrees by correspondence, two from London University, to go with the three he already had.

Mugabe is somewhat of an anomaly since he was raised a devout Catholic and is now a avowed Marxist even though there is evidence that he still practices his religion.

He was known to attend mass during the abortive two-month Geneva peace conference in 1976 but since then, living in Marxist Mozambique and receiving most of his aid from communist countries, it has probably been politic for him not to publicly practice Catholicism. "I have to do my shopping in the East," a friend quoted him as saying.

There is no question about his family's religious fervor, however. His mother, well into her 80s, says the rosary several times daily and his two younger sisters do missionary work. He also has a younger brother who is a teacher.

Friends say the atrocities attributed to Mugabe's party, the Zimbabwe African National Union (ZANU), are the unfortunate fruits of war and not ordered by Mugabe. To many white Rhodesians, he is simple a murderer and a Marxist.

Although he makes no bones about his Marxist leanings, he has toned down that image in the last year, talking more about socialist principles in the manner of a European social democrat.

"We are the view that the resources which God has given us . . . belong to us all," he told an interviewer. "They shouldn't be the monopoly of the Rockfellers and the Fords."

"In Europe, he'd be a Willy Brandt," one politician said, although right now few white Rhodesians, fearful of nationalizations, would probably be willing to believe that.

At one time, Mugabe called his political-economic philosophy by the ill defined name Christian Socialism.

Mugabe did not enter the nationalist struggle until he was in his early 30s. Educated at mission schools and at Fort Hare University in South Africa, he became a teacher first in Rhosdesia and then Zambia and Ghana where he met his wife, Sally, who also will have a seat in the new Parliament.

Returning to Rhodesia in 1960 he joined Joshua Nkoma's nationalist movement but broke with him to found ZANU in 1963 with the Rev. Ndabaningi Sithole, whom he ousted a decade later while still in prison.

His enemies say he is power-hungry while his admirers praise his ability to forgive. They cite his lack of bitterness over the refusal of Rhodesian prison authorities to let him attend the funeral of his only child, a son aged 6, who died of malaria in 1966.

These days his own life is at stake. He survived at least two assassination attempts since his return from exile in January. His mother's house was attacked in December with grenades and gunfire, injuring two of his nephews.

At a meeting last week with Gen. Peter Walls, commander of the Rhodesian military, Mugabe reportedly asked: "Why are your men trying to kill me?"

Walls is said to have replied, "If they were my men, they wouldn't have missed."