The extraordinary and eccentric emphasis on "belief" in Christianity today is an accident of history that has distorted our understanding of religious truth. We call religious people "believers", as though acceptance of a set of doctrines was their principal activity, and before undertaking the religious life many feel obliged to satisfy themselves about the metaphysical claims of the church, which cannot be proven rationally since they lie beyond the reach of empirical sense data.

Most other traditions prize practice above creedal orthodoxy: Buddhists, Hindus, Confucians, Jews and Muslims would say religion is something you do, and that you cannot understand the truths of faith unless you are committed to a transformative way of life that takes you beyond the prism of selfishness. All good religious teaching – including such Christian doctrines as the Trinity or the Incarnation – is basically a summons to action. Yet instead of being taught to act creatively upon them, many modern Christians feel it is more important to "believe" them. Why?

In most pre-modern cultures, there were two recognised ways of attaining truth. The Greeks called them mythos and logos. Both were crucial and each had its particular sphere of competence. Logos ("reason; science") was the pragmatic mode of thought that enabled us to control our environment and function in the world. It had, therefore, to correspond accurately to external realities. But logos could not assuage human grief or give people intimations that their lives had meaning. For that they turned to mythos, an early form of psychology, which dealt with the more elusive aspects of human experience.

Stories of heroes descending to the underworld were not regarded as primarily factual but taught people how to negotiate the obscure regions of the psyche. In the same way, the purpose of a creation myth was therapeutic; before the modern period no sensible person ever thought it gave an accurate account of the origins of life. A cosmology was recited at times of crisis or sickness, when people needed a symbolic influx of the creative energy that had brought something out of nothing. Thus the Genesis myth, a gentle polemic against Babylonian religion, was balm to the bruised spirits of the Israelites who had been defeated and deported by the armies of Nebuchadnezzar during the sixth century BCE. Nobody was required to "believe" it; like most peoples, the Israelites had a number of other mutually-exclusive creation stories and as late as the 16th century, Jews thought nothing of making up a new creation myth that bore no relation to Genesis but spoke more directly to their tragic circumstances at that time.

Above all, myth was a programme of action. When a mythical narrative was symbolically re-enacted, it brought to light within the practitioner something "true" about human life and the way our humanity worked, even if its insights, like those of art, could not be proven rationally. If you did not act upon it, it would remain as incomprehensible and abstract – like the rules of a board game, which seem impossibly convoluted, dull and meaningless until you start to play.

Religious truth is, therefore, a species of practical knowledge. Like swimming, we cannot learn it in the abstract; we have to plunge into the pool and acquire the knack by dedicated practice. Religious doctrines are a product of ritual and ethical observance, and make no sense unless they are accompanied by such spiritual exercises as yoga, prayer, liturgy and a consistently compassionate lifestyle. Skilled practice in these disciplines can lead to intimations of the transcendence we call God, Nirvana, Brahman or Dao. Without such dedicated practice, these concepts remain incoherent, incredible and even absurd.

But during the modern period, scientific logos became so successful that myth was discredited, the logos of scientific rationalism became the only valid path to truth, and Newton and Descartes claimed it was possible to prove God's existence, something earlier Jewish, Christian and Muslim theologians had vigorously denied. Christians bought into the scientific theology, and some embarked on the doomed venture of turning their faith's mythos into logos.

It was during the late 17th century, as the western conception of truth became more notional, that the word "belief" changed its meaning. Previously, bileve meant "love, loyalty, commitment". It was related to the Latin libido and used in the King James Bible to translate the Greek pistis ("trust; faithfulness; involvement"). In demanding pistis, therefore, Jesus was asking for commitment not credulity: people must give everything to the poor, follow him to the end, and commit totally to the coming Kingdom.

By the late 17th century, however, philosophers and scientists had started to use "belief" to mean an intellectual assent to a somewhat dubious proposition. We often assume "modern" means "superior", and while this is true of science and technology, our religious thinking is often undeveloped. In the past, people understood it was unwise to confuse mythos with logos, but today we read the mythoi of scripture with an unparalleled literalism, and in "creation science" we have bad science and inept religion. The question is: how can we extricate ourselves from the religious cul-de-sac we entered about 300 years ago?