At a swift glance, the title of Karen Armstrong’s new book (the subtitle is in very small print) might mislead the casual observer into thinking that she has written a case for the existence of God; that she has unearthed some “proof” unaccountably overlooked by Anselm and Aquinas, or has triumphantly restated the Argument from Design in a way that will smite the enemies of religion as surely as Yahweh’s people smote the Midianites, the Canaanites and those unfortunately named Philistines.

Armstrong has done something far cleverer and more subtle than that, however. The alter­native would have brought her on to a battlefield of her opponents’ choosing, the one on which Richard Dawkins, Christopher Hitchens and Sam Harris have pitched their tents. Those three, she writes, “insist that fundamentalism constitutes the essence and core of all religion”. In fact, she argues, it is “a defiantly unorthodox form of faith that frequently misrepresents the tradition it is trying to defend”.

The God whom Armstrong is discussing is one whose existence cannot be proved in any way to rational satisfaction, not by the ontological arguments of Anselm and Descartes, nor by science, as Newton thought he had. In fact, even to talk of his “existence” is in itself troublesome. The point she makes from the start is that language, being necessarily limited to human comprehension, cannot fully convey anything about God. All statements about Him are therefore at best analogical – when we say He is “perfectly good”, that is only the shadow of a goodness impossible for us to grasp – and any suggestion of literalism is to fall into a gross and idolatrous anthropomorphism.

Although this may come as a surprise to the millions of Christians who entertain thoughts of God as a jovial beardie – a celestial Frank Dobson, if you will – it is familiar territory for any student of theology or philosophy of religion. Which is why Armstrong is right to describe the analysis of the Dawkinsites, who have made the god they wish to dismiss into just such a being, as “disappointingly shallow” and “based on such poor theology”. It is also why the poisoned darts of Armstrong’s critics (see Johann Hari’s review of Does God Hate Women? in the NS of 6 July) fail to pierce her arguments. They are aimed at territory she does not wish to defend.

It may seem as though stating the near-inadequacy of language is a strange point from which to begin making a case for the deity; would not such an argument be, as the philosophers say, somewhat short on “meaningful content”? But Armstrong argues that in Christianity, “until the modern period, nobody thought of confining their attention to a literal reading of the plain sense of scripture”, and notes that the more mystical and transcendent form of Islam, Sufism, was the “dominant mood” in that religion from the 12th to the 19th centuries; and she quotes how the 6th-century Babylonian Talmud instructed the Jews to regard their sacred books: “What is Torah? It is the interpretation of Torah.” Religion was something to be experienced, its books to be chanted and debated, and only through this could a glimpse of its ineffable truths be gained.

The fixing of texts first came about with the advent of printing, which elevated what was on the page above the spoken, physically felt and thus more mutable word, and then with the search for certainty associated with both the Reformation and the Counter-Reformation. Scientific rationalism made religion even more earthbound when the churches welcomed it, believing it could prove that creation must have been the work of a supreme agent. By allowing this to become their new foundation stone, however, they tried to harness a discipline that was to undermine them, and which over the past two centuries has displaced and discounted that part of human experience which cannot be empirically verified or quantified.

Harking back to the Greeks, Armstrong talks of how mythos, a story encapsulating a timeless, eternal dimension, has been edged out by logos, reasoned, scientific thought. Because we see the past through the prism of the present, we fail to acknowledge that the supremacy of logos over mythos is an aberration, and that for thousands of years the two coexisted quite happily; even Calvin was happy for scripture to accommodate science. In more recent times, however, we have denied the force of that “power beyond our knowledge”, as Euripides put it, surrendering instead to that “meddling intellect”, lamented by Wordsworth, which “murders to dissect”.

What we have lost in the process is the peace and joy of “unknowing”, of contemplating that which we cannot properly conceptualise. Confronted by a mystery – “something in which I find myself caught up, and whose essence is not before me in its entirety” – we instantly try to reduce it to a problem, “something met which bars my passage”. Yet some of the greatest scientists and philosophers, the gods of the new scientific rationalist fundamentalists, from David Hume to Albert Einstein, were never so reductionist. The knowledge that “what is impenetrable to us really exists, manifesting itself to us as the highest wisdom and the most radiant beauty which our dull faculties can comprehend in their most primitive forms . . . is at the centre of all true religiousness”, wrote Einstein. In this sense alone, he said, “I belong to the ranks of devoutly religious men.”

This “stunned appreciation of an ‘otherness’ beyond the reach of language”, for Armstrong, constitutes the heart of every religion. Their liturgies and rituals, their myths and legends that explained creation and helped mankind deal with quotidian misfortune and misery, were all constructed to aid adherents in the path towards this goal. And containing as these faiths all do some variant of the “Golden Rule” – do to others as you would have done to yourself – the steps on this path involved charity and compassion, not the intolerance of fundamentalists and their mirror image, the new God-destroyers.

All else, and yes that includes the many terrible things that have been done in the name of religion over the centuries, is distortion, idolatry and misinterpretation. If you accept this, and Armstrong makes a good historic and theological argument that it is so, then who among us would wish to admit this: that they had lived a life so impoverished that it contained no inkling of that wonder and transcendence she wishes us to acknowledge? Her case rests.