This article was in last week's Tablet, behind the paywall but here with permission...

It is sensible to be sceptical of the pronouncements of neuroscience. When you read, say, that brain scanners have found the ‘love spot’ amongst the folds of grey matter, it is probably a case of neuromania, to use the word coined by the neuroscientist Raymond Tallis.

Nonetheless, neuroscience carries weight in our public discourse. Carefully considered, it offers insights into what it is to be human. Although, what is revealed, upon a second reading, often seems not so much like new insights, as old insights re-described with the authority of science. This is particularly true when it comes to matters concerning spirituality.

One crucial phenomenon here is brain lateralisation: the significance of the fact that the brain is not symmetric. Its two hemispheres are structurally, physiologically and psychologically different. They see the world in different ways.

In fact, argues Iain McGilchrist, in his fascinating book, The Master and His Emissary, it is best to think of the hemispheres as two personalities. It often makes better sense to ask what each hemisphere is like, as opposed to how it works.

It is a discovery with deep implications for the study of spirituality. I suspect McGilchrist’s book will prove instrumental in reinvigorating spirituality for an age that has otherwise grown wary of the religious quest. Others appear to think similarly too. Last month, no less a figure than the Archbishop of Canterbury, Rowan Williams, hosted a private seminar with McGilchrist to discuss the ramifications of his work.

The two persons interpretation of brain lateralisation comes from Roger Sperry, the neuroscientist who won the Nobel Prize for his work on split-brain research. The left loves precision. Its purpose in life is to manipulate. It seeks certainty and gains that by building maps of what it has grasped of reality, though like physical maps, the left hemisphere’s charts come with the inherent limitation of being abstracted from the world as it actually is. They are handy fictions.

The right hemisphere serves the ability to make connections and build understanding. It has the kind of personality that enjoys possibilities and novelty. Delighting in pattern, it discovers, though is also able to remain uncommitted about the nature of things. This negative capability, to recall Keats’ expression, allows it to stay alert to the unknown and, therefore, more in touch with reality. It can live with what it can’t understand.

Why two hemispheres, not just one brain? In short, because we need both kinds of attention to survive. The left hemisphere’s narrower focus supports the capacity to control the world. The right offers the capacity to maintain a sustained, open engagement. If the left longs to make the world its own, the right receives. If the left conceptualises, the right is expectant. The two are in a creative tension. Put them together and you have the brilliant capacity, say, to stand back from reality whilst remaining part of it; to have a distance from things without becoming detached. That must have tremendous evolutionary advantage: other animals have split brains too. In this process of right-left-right exchange, human experience deepens. It becomes three dimensional. One seamless self-consciousness is the result of embracing the wills of the two hemispheres.

Here, then, is a first ‘discovery’ that chimes with the traditions of spirituality because this is precisely the kind of awareness promoted in practices such as insight meditation. Mindfulness, as it is also known, cultivates an ability to be aware of thoughts and feelings as well as actually having those thoughts and feelings. As the author of the Visuddhimagga wrote 1600 years ago: ‘The first realization in insight is that the phenomena contemplated are distinct from the mind contemplating them… he can, with further insight, gain a clear understanding of these dual processes…’

It is important to emphasis the necessity of both hemispheres for such full consciousness, as it is tempting to make the reductionist move and simplistically associate the left with the rational and the right with emotion. McGilchrist is keen to stress that it was such popularisation of brain lateralisation that almost ruined the subject for serious science. As he said in a recent talk: ‘Then there was a Volvo ad about the car for your right brain. That did it. From then on, no self-respecting scientist could be found to touch the topic.’

Being ‘right-brained’ does not mean being spiritual. The truth is that the most valuable spiritual insight lives on a knife-edge between intuition and discernment. You need both to keep a balance between what Wittgenstein called ‘saying’ and ‘showing’. This is a second dominant theme in spiritual writers. Denys the Areopagite, for example, stressed such a binocular approach when he remarked: ‘The tradition of the theologians is twofold, on the one hand ineffable and mystical, on the other manifest and more knowable… the ineffable is interwoven with what can be uttered. The one persuades and contains within itself the truth of what it says, the offer effects and establishes the soul with God by initiations that do not teach anything.’ The marriage of the left and right hemispheres could hardly be more precisely expressed.

A third area concerns the importance of the body. ‘Spiritual practice is always embodied when it is most effective,’ explains Fraser Watts, who heads up a research group on embodied cognition in the University of Cambridge. ‘People pray with their bodies as well as their minds.’ Hence a spiritual director is likely not to advise you to contemplate ‘proofs’ for the existence of God to deepen your relationship with the divine, but to go on pilgrimage, attend liturgies and rituals, or introduce discipline and pattern into your life.

This makes sense when it is realised that the right hemisphere is more deeply connected to the body. Both hemispheres have motor and sensory connections with the opposite side of the body. But whereas the left makes maps, the right carries a whole body sense that is intimately linked to lived, affective experience. It is responsible for empathic and emotional connections with others and the world. It is the wellspring of expansive, meaningful and uncertain feeling – which in the theological realm is the pathway to God. Hence, as the author of The Cloud of Unknowing insists, the cloud is pierced by a ‘dart of longing love’, not intellection.

There are many other points of contact between the science and the spiritual, but one more particularly catches my eye. It concerns the way the two hemispheres communicate. This is something of a problem because they speak such different languages. The gulf is bridged largely by processes of inhibition across the structure known as the corpus callosum. It is the inhibitive quality that is so fascinating because what it implies is that the left can only accept what the right has to offer, and vice versa, by a process of unknowing what it had taken to be the case. It must let go and tolerate a new, unsettling and unexpected vision of things. To make the link to the spiritual, it could be said that this mode of communication is a kind of via negativa. To cite the author of The Cloud of Unknowing again, when describing how God might be grasped: what was known must be ‘covered with a cloud of forgetting’.

In his book, McGilchrist musters the evidence to show that the left hemisphere is good at suppressing the insights of the right. Hence an age that fails to understand the spiritual quest, such as ours, may be suffering from a condition known as ‘hemispheric utilisation bias’. The left has, as it were, imposed its view of the world upon us at a cultural level.

That explains why it is often claimed that neuroscience demonstrates we are purely material beings and that consciousness is a delusional by-product of electrically charged meat. But perhaps the truth is precisely the opposite. To put it crudely, a culture enamoured with the insights of the left hemisphere trusts the neuroscience because it is a science. What it is perhaps just beginning to notice is that the science is subtly unpicking the very worldview to which it has been so wedded.