Whatever it is that we call “spirituality” has to go through the brain, the three pound organ under our skulls that has roughly 100 billions neurons, 100 trillion synaptic connections, and the consistency of butter at room temperature. There’s no use trying to understand the philosophical or religious meaning of life if at some point you don’t square up to the biological fact that all our perceptions of meaning interact in some way with this organ.
In order to have a coherent view of human nature, at some point questions like these must be posed: What is the ontological status of a thought? Mere chemicals firing in obedience to the drives of Darwinian survival? A reliable response to something existing independently outside the brain? A gifted participation in the rational nature of God? None of the above?
We’ve known for centuries that the brain, like the rest of the human body, is split neatly down the center into two hemispheres. Only in recent decades, however, have neuroscientists identified not only the different functions of the brain’s hemispheres, but that these two sides of our mental hardware in fact generate radically different ways of perceiving and interacting with reality. The left hemisphere deals with language, logic, systems, precise data, strict definitions, and in general seeks to control things. By contrast the right hemisphere deals with images, metaphors, music, stories, broader contexts, is more inclined to mystery than strict definitions, and more given to care than control.
Here's something I believed for a long time, which much of late modern society also believes: that the skills of the left hemisphere have the best read on the world as it really is, and that modernity's story of scientific liberation from pain and suffering is largely underwritten by left-hemisphere modes of thought. I needed a sharp dose of disenchantment because this belief is only half the picture. It turns out—as demonstrated incisively by the British polymath Iain McGilchrist in his The Master and His Emissary: The Divided Brain and the Making of the Western World—that the right hemisphere produces both our first and last drafts of reality, and that the left hemisphere’s remarkable facility with data and manipulation is a good servant but a terrible master. Far from being liberated by a society that rewards the left-hemisphere techniques of bureaucrats, bankers, lawyers, scientists, and technicians, McGilchrist argues that we have become imprisoned by the left hemisphere’s materialistic, manipulative, overly-specialized way of being.
We need to remember some basic truths about the relationship between our brains and the meaning of life: that images and imagination comes before the precision of words, that care is better than control, that a living mystery is better than lifeless creed, and that stories are often more true than syllogisms. This doesn't mean replaying the reaction of Romanticism to the Enlightenment, biased toward whatever is perceived to be fresh and spontaneous and free of institutional structure. That's an error of an equal and opposite variety. What this means is that we are holistic creatures in need of both hemispheres: just as it takes two eyes to perceive in three dimensions, or as a fruitful synergy happens when a man and a woman make a life together, or as the circle of the moon reflects the greater light of the sun—so God has made a world that flourishes in reciprocity, balance, and wholeness.
If you're looking to deepen your understanding of how spirituality and the brain overlap, several books are helpful:
At the level of theory:
William James, The Varieties of Religious Experience: A Study in Human Nature
Teilhard de Chardin, The Phenomenon of Man
Jonathan Haidt, The Righteous Mind: Why Good People Are Divided By Politics and Religion
At the level of practice:
Martin Lair, Into the Silent Land: A Guide to the Practice of Contemplation
C. S. Lewis, The Screwtape Letters
Caroline Leaf, Switch On Your Brain: The Key to Peak Happiness, Thinking, and Health