SHEIKH SALAH ABU ISMAIL sits in his living room in the Cairo district of Dokki, talking on two telephones at once, an orange receiver clutched in one hand, a white receiver in the other.
He wears a handsome gray gallabiya and an amma, a raspberry-colored tarboosh wrapped in the white turban customarily worn by men of religion in Egypt.
The visitor can hardly get a word in edgewise. When Sheikh Salah gets off the phones, the doorbell rings and a young engineer comes in to ask Sheikh Salah's advice on some personal matters. When the young man leaves, a delegation of well-to-do peasants from the sheikh's constituency in the Nile Delta, which he represents in the Egyptian parliament, arrives on his doorstep.
''It's like this always,'' his teen-age daughter whispers to the visitor, referring to the constant comings and goings at the sheikh's house.
But what makes Sheikh Salah more remarkable than the average Egyptian member of parliament is that he is a Muslim brother and an outspoken critic of the current Egyptian government.
The Muslim Brotherhood is an illegal organization in Egypt. The late President Anwar Sadat threw many of its leaders in jail in September, during his crackdown on religious fanaticism. But many, like Sheikh Salah, still count themselves among its ranks and like him, have strong links with Saudi Arabia and other Gulf countries.
Sheikh Salah has been the guest speaker at May demonstrations sponsored by the Gma'aat Islamiyya, when those Islamic societies controlled student life on Egyptian university campuses in recent years. Those societies are now outlawed. Their leaders and thousands of their members were thrown in jail in September and during President Mubarak's roundup in October after Mr. Sadat's assassination.
Yet Sheikh Salah is still preaching, still a member of parliament, and still castigating the government for its secular practices and its conduct of foreign policy.
And the regime of President Hosni Mubarak is trying to decide what to do about it.
Since the bloody and tumultuous October day that catapulted him into the seat of Egypt's presidency, one of Mr. Mubarak's major concerns has been to neutralize or at least pacify Egypt's Islamic opposition. He has also been trying to root out the violence-prone secret Islamic organizations like the ones that killed Sadat and engineered a virtual insurrection in the southern city of Asyut shortly afterward.
This task has meant a major reversal of government strategy, for up until the last few months of his rule, Mr. Sadat aided and encouraged Egypt's Islamic groups to counter the threat to his government from Egyptian leftists.
Only at the end, when it was ''too late,'' as Mr. Mubarak mournfully reflected in an interview shortly after he took office, did Mr. Sadat recognize the threat the movement itself was posing to his regime and take steps to crush it.
His partial crackdown in September 1981 was meant to serve as a warning to Islamic groups that he would tolerate ''no religion in politics and no politics in religion.'' But it served instead to inflame them further and began a tragic chain of events that led to Mr. Sadat's death.
The concern with the threat the Islamic groups still pose to the state has lurked in the shadows behind Mr. Mubarak's major policy decisions to date. His call for social justice and condemnation of corruption has stolen some of the fire from the sermons of the poor sheikhs. His reconciliation with the opposition parties has created a respectable platform for political dissent and alternative channels for political energies other than the Islamic groups.
Mr. Mubarak has released several of September's detainees, including the leadership of the Muslim Brotherhood and other Islamic activists.
His emphasis on nonalignment has taken some of the sting out of Egypt's close relations with the United States, which the Islamic groups, among others, have charged is encroaching on Egypt's sovereignty.
But most important, Mr. Mubarak is disengaging religion from the political arena.
''Mubarak said I don't want to talk about religion pro or con,'' relates Milad Hanna, a prominent Coptic Christian leader imprisoned by Sadat who, on his release in November, went to visit Mubarak at the Uruba Palace. ''He said: 'Let's put it in the freezer, and let it get colder on its own.' No answer could have pleased me more.''
Unlike Sadat, Mubarak has not exploited the symbolism of Islam to legitimize his rule or increase his popular support. He does not have himself filmed at Friday prayers, or use Islam as a slogan of his regime.
Many Egyptian intellectuals seem to think it will be successful in turning popular energies away from the fundamentalist sheikhs toward a secular debate and discussion on development.
But much depends on Mubarak's ability to deliver on the many promises he is making to the public.
He comes as Egypt's third President to a nation that has grown weary of hit-or-miss government planning, revolving-door cabinets, and entrenched ruling elites that do not represent the aspirations of the masses. Egyptians are tired of the propaganda machines of secular governments experimenting with different ideologies and development that seems to mean only becoming more Western.
''There are many different depths or layers in our national consciousness,'' says Hassan Hanafi, a professor of Islamic philosophy at Cairo University.
''The first is what you see on the streets of Cairo, the indifference, the apparent depoliticization, the concern with getting the daily bread.
''A second, deeper motivation is socialism, Arabism, Nasserism, and nonalignment.
''The third depth is Islam, maybe the Egyptian has had enough of the experience of trial and error (with government), including Nasserism. If a man is exposed to Islam as his salvation, he will go along. If Islam is connected somehow with his dreams, that would be his dream. If a man is asked to choose between two and three, he would follow Islam and sacrifice his Nasserism.''
Dr. Hanafi passionately believes in Islam as the engine of social change. ''Revolutionary Islam reconstructs the belief systems of the masses. It gives a new system regarding problems of development. I am trying to be the bridge between Islam, social justice, and development.''
Because of his maverick views and criticism of the governmentin the last years of Sadat's rule, Dr. Hanafi was not allowed to teach Islamic subjects at the university. During the September crackdown he was transferred. A recent presidential decree has restored him to the university.
Muhammad Abdul Qouddous, a younger member of the Muslim Brotherhood who was imprisoned in September by Sadat and recently released, tries to explain why, coming from a long family line of liberal, secular journalists, he chose to veer off onto an Islamic path.
''In [Gamal] Nasser's days we had the problem of a dictator. In Sadat's days we had social problems, the gap between the very rich and the very poor. We want to change now in the name of Islam.''
''I am convinced in the Islamic way. I am happy. With Islam there is a basic thing. That religion is a total way of life, and not just something between me and God. Sadat said 'no religion in politics and no politics in religion.' I say , no, 'religion is politics and politics is religion,' and Islam says that.''
Mubarak is counting on journalists and the political parties to cut the Islamic groups' message down to size, by challenging them to convert vague slogans into a blueprint for action on Egypt's development problems like housing , inflation, and birth control.
''Hosni Mubarak should remain the arbiter,'' says one prominent Egyptian political analyst. ''Mubarak himself should not debate them.''
The Islamic leaders who have been released from prison have called for a dialogue with the government. Omar Tilmessani, the aging leader of the Muslim Brotherhood, which represents the main body of sentiment in Egypt's diverse Islamic movement, has renounced the use of violence and calls for realizing his ideal of a theocratic Islamic state by preaching and setting a personal example.
An intense internal debate is going on within the brotherhood on whether to become a political party and operate within that framework, or to hover on the fringes as a powerful interest group, pressuring the government to enact Islamic law.
Until now, the brotherhood leadership has refused to be co-opted into the government structure. In a recent interview with al-Mussawar magazine, Mr. Tilmessani gave the reason.
''We rejected becoming a (political) party because parties have a specific way of working and because a party has a program it tries as much as it can to implement. And we don't have a program or a method, because we adhere to the Book of God and the Sunna (recorded sayings and doings) of his prophet. It satisfies us that any person from any party comes to implement the shariam [law] of God, and we support him, and don't oppose him.''Mr. Tilmessani refused a seat to the advisory Shura Assembly created by Mr. Sadat 11/2 years ago and resisted registering the brotherhood as a social or charitable association at the Ministry of Social Affairs. Sheikh Salah has run for his parliamentary seat as an independent, although he is a member of the brotherhood.
In any case, Egyptian governments have traditionally been wary of granting Islamic groups legitimacy. Egypt is, after all, an overwhelmingly Muslim country and deeply religious. To establish an Islamic party would put the other political parties, including the ruling party, on the defensive as being ''less'' or ''anti-'' Islamic. Even at the height of Sadat's flirtation with the Islamic groups, at most he sought to accommodate them by pushing for partial implementation of Islamic law in Egyptian life and allowing the Muslim Brotherhood to publish a monthly magazine to express its views.
The Muslim Brotherhood still has not been officially recognized by the state as a legal entity, and in a recent newspaper interview Mubarak maintained he would not allow the formation of an Islamic party. He is reportedly debating whether to allow the group to reopen its magazine al-Dawa, which had printed several fiercely antigovernment and anti-Christian articles before it was closed down in September.
But even the Muslim Brotherhood, though it is a semi-institutionalized umbrella organization, does not encompass the multitude of religious groups in mosques all over the country.
Because of the peculiarly democratic nature of Sunni Islam in Egypt, in contrast to the hierarchy of the Shiite mullahs in Iran, there is no supreme religious authority in the country.
''Islam does not have a supreme religious authority,'' says Sheikh Gad Haq, the stately minister of waqfsm (religous affairs) and former Grand Mufti of Egypt. ''The sheikhs at the al-Azhar (Egypt's 1,000-year-old seat of Islamic learning) are specialized in studies. . . . They are guides in clarifying judgments.''
Of Egypt's 45,000 mosques, only 5,000 are run by the government. Last September, Sadat tried to exert greater control over private mosques by putting them under the supervision of the Ministry of Waqfs. But as officials readily admit, they do not have the money or the trained personnel to appoint a government sheikh or even an inspector to every mosque. The mosques, therefore, remain effectively in private hands and host preachers the congregation chooses.
Even government control of the mosques is not enough to stifle political dissent. Sheikh Kishk, a popular blind preacher also arrested in September and recently released, is employed by the Ministry of Waqfs and has preached in a government mosque. Even when his sermons became politically embarrassing, he was so popular the ministry did not dare to fire him or transfer him from his post.
Now that Sheikh Kishk has been freed, his tape-recorded sermons are once more blaring onto Cairo streets from sidewalk kiosks and juice stands.
Although the state security organs remain on the alert, Mubarak has deduced that the way to overcome the Islamic threat is not more policing action. When provoked, even the more peaceful Islamic groups have become violent.
If Mubarak pushes his Nasserite revival too far and does not give the Islamic movement a forum, the Muslim Brotherhood and other Islamic groups will oppose him.
To debate them is an option, if the Islamic groups respond.
''There is not enough trust,'' says Ahmed Heikal, dean of the Dar al-Uluum faculty at Cairo University, which teaches the history and development of Islamic thought. Dr. Heikal has often tried to debate the young men and women of the Islamic societies at the university.
''When they have a question, they go to people like themselves, like Sheikh Kishk. They don't go to the sheikhs of al-Azhar because they are government employees and say what the government says. They don't come to me because I wear a suit and was educated in Europe and speak a foreign language. There is a gap.''
Although most observers here would agree that President Sadat's assassination eased mounting tensions in the country, it is by no means certain that the strength of the Islamic movement is waning.
''Even if they are in a weakened position now,'' says one Egyptian Marxist, ''if they are given a forum they can grow very rapidly.''
Some of the older members of the movement have signaled that they are ready to deal with the government. The younger members are more rebellious, angry, and impatient.
''All the elements of the Sadat regime are still present,'' says Muhammad Abdul Qouddous. ''All the millionaires are still there in the ruling party.''
Like most Egyptians, the members of the movement are biding their time, waiting to see what Mubarak will do, and where the policies he is charting will lead.
''Egypt is at the crossroads,'' says Ali Dessouki, a professor of political science at Cairo University. ''It could go either way.''