The activity that we call religion is complex. Religious and non-religious people alike often share the same misperceptions. Today in the west, it is often assumed that religion is all about the supernatural and that it is inseparable from belief in an external, personalised deity. Critics claim that religion encourages escapist fantasies that cannot be verified. The explosion of terrorism (which is often given a religious justification) has convinced many people that religion is incurably violent. I have lost count of the number of times a taxi driver has informed me that religion has been the cause of all the wars in history.
Yet we find something very different when we look back to the period that the German philosopher Karl Jaspers called the "Axial Age" (c.900 to 200BCE) because it proved to be pivotal to the spiritual development of humanity. In this era, in four distinct regions of the world, the traditions that have continued to nourish humanity either came into being or put down roots. Hinduism, Buddhism and Jainism emerged in India; Confucianism and Taoism in China; monotheism was born in Israel; and philosophical rationalism developed in Greece. It was a period of astonishing creativity; we have never really succeeded in going beyond the insights of such sages as the Buddha, the mystics of the Upanishads, Confucius, Lao-tzu, and the great Hebrew prophets. Rabbinic Judaism, Christianity and Islam, for example, can be seen as a later flowering of the religion that had developed in Israel during the Axial Age.
Despite interesting and revealing differences in emphasis, these traditions all reached remarkably similar solutions. They can, perhaps, tell us something important about the structure of our humanity. The God of Israel was an important symbol of transcendence, but in the other Axial faiths the gods were not very important. Confucius discouraged speculation about spirits and the afterlife: how could you talk about other-worldly phenomena, when there was so much that you did not understand about earthly matters?
During the Indian Axial Age, the ancient Vedic deities retreated from the religious imagination. They were seen as unsatisfactory expressions of the sacred, and were either demoted to human status or seen as aspects of the psyche. Many of the Axial sages were reaching beyond the gods to a more impersonal transcendence - to Brahman, Nirvana or the Tao - that was also inseparable from humanity. Yogins and Taoists did not believe that their ecstatic trances represented an encounter with the supernatural, but regarded them as entirely natural to humanity. Later, the more sophisticated theologians in all three of the monotheistic religions would make similar claims about the experience of the reality that they called God.
None of these sages was interested in dogma or metaphysics. A person's theological opinions were a matter of total indifference to a teacher like the Buddha. He insisted that nobody should ever take any religious teaching, from however august a source, on faith or at second hand. One of the Buddha's disciples pestered him continuously about metaphysics: was there a God? Who created the world? He was so preoccupied with these matters that he neglected his yoga and ethical practice. The Buddha told him that he was like a man who had been shot with a poisoned arrow but refused to have any medical treatment until he discovered the name of his assailant and what village he came from: he would die before he got this perfectly useless information.
The Taoists were also wary of dogmatic conformity; they believed that the kind of certainty that many seek in religion was unrealistic and a sign of immaturity. Eventually, the Chinese preferred to synthesise the schools which had developed during their Axial Age, because no single tradition could have the monopoly of truth. In all four regions, when a sage started to insist upon strict orthodoxy, this was usually a sign that the Axial Age was drawing to a close.
The prophets of Israel were more like political commentators than theologians; they found the divine in analysis of current events rather than metaphysics. Jesus, as far as we know, spent no time discussing the trinity or original sin, which would later become so important to Christians; and the Koran dismisses theological dogmatism as zannah, self-indulgent guesswork that makes people stupidly quarrelsome and sectarian.
Religion was not about believing credal propositions, but about behaving in a way that changed you at a profound level. Human beings have always sought what the Greeks called ekstasis, a "stepping out" of the mundane, in moments when we feel deeply touched within and lifted momentarily beyond ourselves. The Axial sages all believed that if we stepped outside of our egotism and greed, we would transcend ourselves and achieve an enhanced humanity. Yoga, for instance, one of the great spiritual technologies of the Axial Age, was a formidable assault on the ego, designed to take the "I" out of the practitioner's thinking.
But the safest way to achieve this ekstasis was by the practice of compassion. Compassion - the ability to feel with another - was not simply the litmus test of any true religiosity, but the chief way of encountering the ineffable reality of Nirvana, Brahman, God and Tao. For the Buddha, compassion brought about ceto-vimutti, the "release of the mind" that was a synonym for the supreme enlightenment of Nirvana, a sacred realm of peace in the core of one's being.
All the Axial religions, in different ways, regarded what has been called the Golden Rule as the essence of religion: "Do not do to others what you would not like them to do to you." Confucius was the first to formulate this maxim. It was, he said, the thread that pulled all his teachings together and should be practised all day and every day. Five hundred years later, Rabbi Hillel was asked to sum up the whole of Jewish teaching while he stood on one leg. He replied: "That which is hateful to you, do not do to your neighbour. That is the Torah. The rest is commentary. Go and study it."
The Chinese sage Mo-tzu (c.480-390) insisted that we had to have jian ai, "concern for everybody". The priestly authors of Leviticus urged the Israel-ites to love and honour the stranger; the Buddha taught layfolk and monks alike a method of meditation called "the Immeasurables", in which they systematically extended benevolent thoughts to the four corners of the world. Jesus told his disciples to love their enemies. This impartial sympathy would break down the barricades of egotism, because it was offered with little hope of any return.
If a ruler practised jian ai, Mo-tzu taught, war would be impossible. The Axial religions all developed in regions that were convulsed by violence on an unprecedented scale. Iron weaponry meant that warfare had become more deadly; states had become more coercive; in the market place, merchants preyed on each other aggressively. In every case, throughout the Axial Age, the catalyst for religious change was always a disciplined revulsion towards this violence.
In the 9th century, the ritualists of India systematically extracted all the violence from the sacrificial ritual, and in seeking the cause of aggression in the psyche, discovered the inner self. Renouncers, Buddhists and Jains all insisted that ahimsa, "harmlessness", was an indispensable prerequisite to enlightenment. In the Tao Te Ching, Lao-tzu pointed out that violence could only elicit more violence. The sage-ruler must always seek to bring a military campaign to a speedy end: "Bring it to a conclusion, but do not intimidate." Some of the gospels present Jesus as a man of ahimsa who taught his followers to turn the other cheek.
Socrates, one of the greatest figures of the Axial Age, also condemned retaliation as evil. In general, however, the Greeks did not eschew violence. Ultimately, they did not have a religious Axial Age. Their great transformation was philosophical, scientific and mathematical, and pagan religion continued to flourish in Greece until it was forcibly replaced by Christianity in the 5th century CE.
Compassion is an unpopular virtue. All too often, religious people have preferred to be right rather than compassionate. They have shielded themselves from the demands of empathy by making secondary and peripheral goals - such as theological correctness or sexual orthodoxy - central to their faith. As the Chinese sages pointed out, vehement professions of belief were essentially egotistic, a pompous trumpeting of self, and, therefore, they impeded enlightenment. Denominational chauvinism, like nationalism, should also be seen as a form of collective egotism or, in monotheistic terms, idolatry.
Nevertheless, in our torn, conflicted world, we need to revive the Axial ethos. This does not require orthodox belief and need not involve the supernatural. In the Axial Age, individualism was beginning to supersede the older tribal or communal expressions of identity. The sages were trying to moderate the clash of competing egos and they were all concerned about the plight of society. We are still rampant, chronic individualists, but our technology has created a global village, which is interconnected electronically, militarily, politically and economically. If we want to survive, it makes practical sense to cultivate jian ai. We need to apply the Golden Rule politically, and learn that other nations, however remote from our own, are as important as ours.
Karen Armstrong is the author of The Great Transformation: the world in the time of Buddha, Socrates, Confucius and Jeremiah (Atlantic Books, £19.99)