Unitive Neuroscience

I once wrote a line that I arrived at somewhat flippantly, but which deserves closer examination: “We look into another’s eyes and know that the consciousness with which we gaze in is the same as that which shines out.”

When I wrote this, I did not mean to speak with mere mystical sensibility. I do consider myself a mystic, but I don’t expect my personal experiences to sway anyone but me. While my inner life certainly informed those words, I was actually drawing on something far more concrete: my background as an ophthalmologist and my understanding of the human visual system.

The Architecture of Sight

Imagine my friend and I are sitting together in a teahouse. The light reflecting off my face is refracted by the cornea and lens of my friend’s eyes, casting a sharp image onto the retinal surfaces at the back of their eyes.

At this moment, a pattern of photons strikes photo-sensitive cells. There, the light is detected by proteins loaded with a derivative of vitamin A, causing the voltage across the photoreceptor cell membranes to alter in response to the illumination. This electrical shift communicates with a complex network of information-processing cells within the thin architecture of the retina itself.

From there, the processed data is propagated out of the eye via the optic nerve and conveyed to a central brain structure called the thalamus. Here, the signals from both eyes are brought together and aligned; for example, the signals representing the left side of my face, detected by both of my friend's eyes, are precisely matched.

From the thalamus, via fibers traveling to the visual cortex, the data reaches the back of my friend’s head. Cortical tissue then analyzes the patterns, defining edges, motion, colors, and depth. This processing occurs point-by-point, analyzing my eyes, nose, and mouth separately before higher cortical levels weave them back together into a coherent whole.

As this processing continues, what we call meaning arises. The fusiform gyrus recognizes the specific geometry of my face, bringing a sense of my unique identity into my friend’s mind. Simultaneously, the emotional regions of the brain weigh in to interpret my facial expression.

The end result of this vast, interconnected cellular effort is that the subjective, inner world of my companion lights up with my image, accompanied by an empathic sense of my mood and memories of our shared history.

The Shared Architecture

The science behind this process is accurate and replicable. Yet, even though these physiological steps are well-mapped, the ultimate result remains stunning—even awe-inspiring.

What is more, my friend and I are experiencing each other in consciousness through the exact same neurological processes at the exact same time. Despite our differences in genetics, education, and life experience, we possess the identical biological machinery of awareness. It is safe to say, therefore, that the consciousness shining out of my friend’s eyes is of the very same nature as the consciousness looking in from mine.

But my original statement went a step further. Is a consciousness of the same nature also the exact same entity? Are we, in fact, one?

A Single Room?

Because of our distinct identities, and because my companion knows things I can never know, we obviously do not share a single, monolithic mind. But do our minds connect at some deeper, subterranean level? William James captured this possibility beautifully with a botanical metaphor:

“The maple and the pine may whisper to each other with their leaves... But the trees also commingle their roots in the darkness underground... Just so there is a continuum of cosmic consciousness, against which our individuality builds but accidental fences, and into which our several minds plunge.”

Skeptics may argue that James's metaphor is comforting but empirically untestable, attributing my belief in it to personal bias. But those who insist we are entirely isolated neurological islands are also operating from their own background assumptions and biases. Because neither absolute separation nor absolute unity can be strictly proven or falsified, both positions sit on equal philosophical footing.

Yet, whether we agree with James’s commingled roots or not, isn’t it remarkable that life serves up a vibrant inner world where we can see one another, share each other’s pain, and offer love? Isn't something profound inherently shared, regardless of how the subterranean plumbing works?

We may not share the specific content of our daily awareness, but we absolutely share the mysterious experience of awareness itself. That common ground is more than enough for me to feel, in the deepest way, that when I look into another's eyes, the consciousness with which I gaze in is the very same as that which shines out.