He chuckles when he boasts of the Netanya bombings - "the biggest military attack ever inside Palestine," he says - and giggles when you ask if he knew in advance of the slaughter. Express your surprise that he neither greets visitors with "Salam Aleikum" nor quotes from the Koran, and he grins. "We are not talking about theology - we are talking about politics and military things."
For Dr Shkaki, Netanya was not murder most foul but a military "operation", of which he says there will be more in the coming weeks. "We will continue our struggle," he says. "A few years ago, we used knives. Three months ago, we used a bicycle bomb after Hani Abed [the Islamic Jihad journalist allegedly blown up by Israeli agents] was killed by Mossad. Now we have changed our style. We know the Israelis are very sophisticated too. It's more difficult and expensive for us to get explosives than for anyone else in the world, but if you want to, you can do it ... " And he laughs again, insatiably, fearfully, such dark gibes, such sinister merriment.
Was he given advance warning of the suicide bombings at Netanya? "This is something I will not talk about." Another frightening smile. How did he respond to this bombing and to the slaughter of Israeli civilians in the Tel Aviv Hamas suicide bombings last October? Hamas should be asked for an explanation of the Tel Aviv bombing, Dr Shkaki replies. Netanya was a "military" target. Then the response turns to rapid fire.
"For us in Islamic Jihad, if we give orders to our mujahedin, we are talking about military and settlement targets. But in war many things can happen. We Palestinian people face an organised army and most of our losses are civilians ... it is a war. We arenot attacking Americans or Europeans. We are not even attacking Jews or Israelis outside Palestine. We are only defending our right to live in our homeland ... We lived in peace with Jews for centuries. Why do the Jews want to live in a colonialist state?They can live in Europe or America ... I have no problem with Jews ... But I will fight occupation."
The room is banal; a third-storey office in the Palestinian camp at Yarmouk on the outskirts of Damascus, decorated by a model of Al-Aqsa mosque, a lithograph of Hani Abed and a framed photograph of two "martyrs" killed by the Israelis in southern Lebanon. Even his career sounds a trifle mundane at first hearing.
Born Gaza, 1951, his family originally from Rehovot, near Tel Aviv, in present-day Israel, a mathematics teacher in Jerusalem 1970-74, a medical student in Egypt until 1981, a doctor at Augusta Victoria Hospital in Jerusalem until 1983.
Dr Shkaki's English flowers and eclipses during conversation, along with his obsessive laughter and his desire to demonstrate his knowledge of English literature. "Before I am a politician and the leader of Islamic Jihad, I am a human being and a poet also - yes, I read your literature: Shakespeare, Dante, T S Eliot, Ezra Pound ... "
When I suddenly ask Dr Shkaki if he speaks Hebrew, there is a nervous shuffle from one of his underlings before another of those infuriating chuckles. "I learned Hebrew when I was in prison but it is very weak. How did you know I spoke Hebrew?" I tell DrShkaki that he pronounced "Rehovot" with an Israeli accent, that this gave him away. On the shelf beside his desk there is also a Hebrew dictionary. He says he wants to improve his knowledge of the language - a strange ambition, it occurs to me, for a man who personally knew one of the suicide bombers who killed the 21 Israelis last Sunday.
"Yes, by chance I knew one of them, Salah Shaaker. When he was 14 years old he used to come to my home because I knew his big brothers - who were in the nucleus of our Islamic Jihad movement in Egypt. But I myself did not choose the bombers. This was thework of the military ... the two mujahedin, Shaaker and Anwar Soukar, knew each other very well. Before it happened, they went to the scene of the operation and studied it carefully.
"At an exact hour and day, they went from Gaza to Tel Aviv, and from Tel Aviv to the military bus station, which was very well protected. No civilian can enter. But beside the military station there was a small coffee shop where some soldiers go to have coffee or eat. It's easy to enter the coffee shop but it's difficult to enter the station. They co-ordinated between them. The first was to enter the coffee shop and blow himself up. The second was to stay outside and wait for the soldiers , then enter the group and blow himself up."
There are no smiles now. "Before the intifada [the Palestinian uprising], it was difficult to recruit for our military cells. But after the intifada, many of the young wanted to do military operations. After the Oslo accords [between Israel and the PLO],this increased. Some of these youths who come to us insist they want to lead a suicide operation. Maybe it's because they are influenced by the teachings of Islamic Jihad. We choose only those who insist. My orders are to convince them not to go, to test them. If they still insist, they are chosen."
It was in Egypt as a medical student that Dr Shkaki founded what was to become perhaps the fiercest of all Israel's modern-day enemies. "It started as a dialogue in the mid-1970s," he says. "I was a member for a few years of the (Egyptian) Muslim Brotherhood but I rejected their conceptions and moved to new ideas. As Palestinian students, we would discuss Islam and Palestine and we saw two categories of Palestinian: the nationalists, who talked about liberating Palestine but who forgot about Islam, and the traditionalists, who talked about Islam and an Islamic state but who forgot about Palestine. We had to solve this problematic issue, to make the crossing-point between nationalist and Islamist. So we talked about Islam, Palestine and Jihad [holy struggle] - Islam would be the idea we would start with, Palestine the goal to liberate and Jihad would be the way, the method."
Around 50 Palestinians grouped themselves around Dr Shkaki in Egypt and formed the organisation of Islamic Jihad on their return. Dr Shkaki was leader even as he worked as a doctor in Jerusalem. He married - the family has two boys and a girl - and published a magazine, Islamic Vanguard, which cost him a year in Gaza jail.
In 1986 he was arrested again and sentenced to four years in prisons at Ashkelon and at Nafah in the Negev desert. After serving scarcely two years of his sentence, he was deported to Lebanon - apparently on the personal orders of Yitzhak Rabin - and made his way to Damascus but only after visiting Tehran, where he met Ayatollah Khomeini six months before the spiritual leader died. He has returned to Tehran four or five times since - once for a conference at which the Iranians pledged millions of dollars for the Palestinian "resistance".
As for Damascus, Dr Shkaki insists that he receives no "material support" from Syria. After the Netanya bombing, the US Secretary of State, Warren Christopher telephoned Farouk al-Sharaa, the Syrian Foreign Minister, to ask Syria to give "no further sanctuary to terrorists".
Dr Shkaki says he is untroubled by Mr Christopher's demand. "Damascus is a capital open to all Arabs. I came as an Arab citizen. Our presence here is not an official one like other [Palestinian] factions. We don't have official relations with the Syrian government ... after Christopher phoned to Dr al-Sharaa, the Syrians haven't talked to me and I haven't talked to them. We don't have institutions or infrastructure here. It is very easy for me to move to another capital if that is in Syria's interests."
Leading article, page 14