Born in 1944, Armstrong began her journey to faith as a Roman Catholic nun but left her order in 1969 when she embarked on a doctoral study of Lord Tennyson.
She later left academia and, following a brief teaching stint, began researching the life of St Paul for a documentary series.
This eventually led to a re-examination of religions and several books on the subject including A History of God: The 4000-Year Quest of Judaism, Christianity and Islam; Jerusalem: One City, Three Faiths; Muhammad: a Biography of the Prophet; The Battle for God; and Islam: A Short History.
Armstrong is currently teaching Christianity at London's Leo Baeck College for the Study of Judaism. Her latest publication focuses on the birth of compassion in the pre-Christian Axial Age.
Firas Al-Atraqchi, Aljazeera.net's contributing editor, recently caught up with Armstrong in Cairo where she was delivering lectures on religion as part of the American University in Cairo's English public lecture series.
Aljazeera.net: What is the common denominator linking all the faiths you have studied?
Armstrong: I would say compassion and the Golden Rule, ("don't do to others as you would not have done to you") which is what they all teach. I was with the Dalai Lama a couple of months ago and he said all religions teach kindness. He said: "My religion is kindness."
Compassion doesn't mean we have to feel warm affection for people - we have to learn to feel with them, to dethrone ourselves from the centre of our world and put another there.
We have to do that globally to learn other nations, other people, are as important as ourselves. If we don't like people speaking against our culture, bombing or terrorising us, we shouldn't do it to others.
Which direction is Islam taking in the West? Why does there seem to be turmoil for Muslims who have lived for generations in the West?
At the moment, Muslims are reeling under the impact of 9-11 and it's very uncertain where they are going. Some have put their heads down and don't want to raise them above the parapet at all while others are horrified by what happened but find their voices are not listened to.
Some - as we have seen by our own British bombers - are appalled by the pictures coming out of Guantanamo, Iraq and Abu Ghraib and daily from Palestine. This feeds into an alienation that they feel from their own British culture they were brought up in.
"Since 9-11, hostility towards Islam has accelerated which is endemic in our society"
Since 9-11, hostility towards Islam has accelerated which is endemic in our society. On the other hand, these images of people being beheaded on TV just reinforce these old stereotypes and make it more difficult for Muslims to feel at home.
It is very difficult to know where they are going.
But there is no clash of civilisations in an ontological way.
At the beginning of the 20th century when Muslims first began to encounter the modern West, they recognised it as congenial to their own traditions. But then bad foreign policy - Palestine, Suez, the support of tyrannical dictatorial rulers, and the rush for oil (which often meant that ethics were overlooked) - has alienated many in the Muslim world and made them feel the West is a double dealer.
On the part of Western politicians, there is a failure to see the contradictions in their own policies. You can't be talking about free speech one moment and threatening to bomb Aljazeera tomorrow. This is not consistent.
I was with Desmond Tutu - I am on a United Nations committee called Alliance of Civilisations which tries to bring people together - and he was saying how appalled he was that Tony Blair was trying to push through a law allowing detention without trial for 90 days.
Tutu recalled when they were fighting apartheid in South Africa the British had always been coming to the government and telling them you can't put people in jail without trial.
You can't be democratic or part of the modern world if you practise this sort of thing and yet here they are doing that, never mind Guantanamo Bay where people have been held for a very long time without trial.
The race riots in France and Australia, they involved Arab and Muslim youth. Is this a harbinger of things to come?
I don't know much about the riots in Australia as I have been travelling, but the French riots had very little to do with Islam and much more to do with deprivation and ostracising, racism. There's been trouble brewing in France for so long with the immigrant communities which are kept in some type of ghettoes.
Similarly, with our British bombers, they were kept in a part of Yorkshire, in northern England, that I have never visited. And that is indicative - I wouldn't go there.
But there are places where Pakistani youths are at the bottom of the pile. They have very little chance for advancement. There were in 2001 race riots there, before 9-11. It is race and second classism, a sense that there is no way they can make their way forward in society.
The riots in France were not
Muslim riots, says Armstrong
Nothing much was done after the 2001 race riots in the UK. And they are now beginning to reap the rewards of that. Disaffected people look at images coming from Guantanamo Bay and Iraq and this ignites something in their soul.
We are not talking about a universal Islamic Jihad and it was wrong of the papers to call these Muslim riots; these were just riots about deprivation and discrimination.
In your book, Battle for God, you wrote that fundamentalist religious movements claim God as their own. What are the similarities and differences between the various fundamentalist movements?
I've concentrated only on the ones in Judaism, Christianity and Islam. Most of them began in fear - a fear of annihilation. All groups are convinced that modern secular liberalist society is going to wipe them out.
This is true across the board.
When they feel that their backs are against a wall, that's when they become aggressive, defensive and worried.
A profound hinging on this is a loss of identity - people not knowing where they are and feeling their values have been marginalised and kicked out of the way.
This produces a sense of frustration and impotent rage. They have a desire to bring God and all religion back to centre stage.
This expresses itself in an exaggerated vision of the enemy; all of them have cultivated blown-up versions of the enemy which reflects a great deal of their own sense of menace.
In some cultures, this fear and dread is hardening into rage and it was quite clear when I finished this book; some fundamentalism was becoming more extreme and moving into a new phase.
Why is Christian Fundamentalism such a powerful force in North America?
It has gradually been making its way to the forefront and many in the US feel alienated by the secularist, intellectualist, and sophisticated discourse of New York, Harvard, Yale and Washington, DC.
Many people in small town America have for a very long time felt colonised by this ideology, just as colonised as people in Egypt felt by the British or in Syria by the French.
There is therefore a struggle. All culture is always contested. Since the 1970s there has been a concerted movement to bring what they call Old Time Christianity back to centre stage, back to the position it held before modernity really took root in 20th-century America.
People like George Bush - he isn't as stupid as he is often depicted, but he is not a great intellectual - represent many of the values of small town America. He has simplistic views of the Middle East; he's hardly ever stepped foot out of the country [before becoming president]. He's not very typical even though he comes from a very rich family; nevertheless he seems to speak for small-town America.
They have used the democratic and political process very skilfully to come from a marginalised position and over the years bring themselves back to centre stage.
It does not have universal support. In the last election, America was split pretty evenly down the middle and there are Americans who abhor this type of discourse. There are people in the Democratic party who are beginning to create a religious discourse on the left. Jim Wallace is doing that and a rabbi in San Francisco - Rabbi Lerner - has just written a book called The Left Hand of God to reclaim religion.
Americans at the moment seem to be more attuned to a religious than secular discourse.
Can you tell us about your new book focusing on the Axial Age?
I just finished it and it will be out in the UK in March and in the US in April. It is already out in Holland.
The Axial Age is the period from 900 to 200 BCE when all the world's religions which have continued to nourish humanity came into being or had their roots. You can consider Christianity and Islam as later flowerings of the Axial Age ideals of monotheism.
This included the emergence of Confucianism and Taoism in China, Hinduism, Buddhism and Jainism in India.
In Europe, you had the Greeks and philosophical rationalism.
It is not just an exercise in spiritual archaeology, because I hope the book will give some indications of perhaps where we may be going wrong today. It seems to me that in our various institutions we are creating exactly the kind of piety people like the Buddha wanted to get rid of.
The essential teachings of the Axial Age were in every case - except for Greece - a rejection of violence. And as a consequence of that the cultivation of compassion and the Golden Rule "don't do to others as you would not have done to you".
That seems to be the basis of religion; they weren't interested in metaphysics or doctrine or orthodox theology at all.
Some have called you a healer idealist while others point to your description of Islam and say you must be a Muslim. How do you describe yourself?
I wouldn't say I am an idealist because I am far too pessimistic to be an idealist. But I have a strong sense of dread, a prickly feeling that we have been here before and we can't go down this road again.
I first got it during the Salman Rushdie crisis - a feeling that in Europe we have been here before. We have cultivated a distorted vision of a people for a thousand years and this ended in the death camps in the 1930s. And we can never go down this road again.
When I started to hear people talking in this loose-lipped way about Islam, I felt a sense of real fear that somebody, even if it had to be me, had to correct these perceptions.
Furthermore, I really admire the Muslim tradition so much. The Prophet Muhammad is the most magnificent example who inherits the most appalling situation - in Arabia at the time there was a bloodbath - and brings peace out of it. And at a great personal cost to himself.
And not only that, but he bequeathed to humanity a scripture that has helped millions of human beings to make sense of their lives.
To have such a combination of very strong spiritual genius with political genius is extraordinary. So there is that admiration.
At the height of Islam's power, Muslim theologians were so pluralistic and daring and affirmative and inspiring; people like Ibn Arabi and Rumi.
I was very alienated from religion by my own experiences as a young nun and wanted nothing to do with religion.
But it was the study of Islam and Judaism, but Islam particularly, that brought me back to a sense of what religion could be at its best.
It gave me an entirely new perspective on things. Even though I am not a Muslim, I have absorbed so much of Islam that it has become a part of me.
I used to describe myself as a freelance monotheist because I draw inspiration from all - I cannot see any of them as superior. And that has now spread to Buddhism and all the rest.
I see all of them just equal, each with its own genius and with its own flaws.
At the moment, I would describe myself as convalescent; recovering from a bad religious experience by the study of these other traditions which continue to inspire me and feed me.
So your books, then, can be considered a spiritual quest?
Yes, yes certainly.
Have you found God?
Oh, yes. But that word - God - is not easy to define and once you do define it, what you really have is a projection because, Allahu Akbar, God is Greater than anything we can conceive. I see my study as a form of prayer.
When I am working at the library or at my desk, I have moments where I am deeply touched within and lifted momentarily beyond myself.
The discipline of trying to put myself out of my post-enlightenment 20th-century rationalism and the feeling of superiority and into the mind of the Prophet and the mystics of long ago teaches me about compassion and to feel with others.
And that spills over into my personal life. I get very upset now by unkindness in any form. I have a thinner skin than I used to have.
So have I found God? As the Chinese would say: "I am on the way." The Now is the point; what's important is the why you're actually on the way and not to be so concerned by the destination.