Updated: Feb 19, 2021

They arrive at dusk, as if from nowhere. As I lean over the balcony edge, camera in hand, they emerge like stars from the gathering dark of the magenta sky, bursting into existence in the air outside my home. Bats. Three of them.

Tiny, erratic creatures, they rush back and forth with boundless energy, almost touching my outstretched face then receding again in a flash, turning endlessly back upon themselves in crazed knots. They are hunting, chasing unseen insects through the first fresh evening of the spring, feeding upon some of the thousands of flies and moths they must eat every night. In their need for these numbers, these creatures of the night are really heralds of spring. They emerge only when the insects do, around this time each year when the equinox passes and the northern hemisphere leans into the sun’s heat.

I am at the perfect height to watch them, level with the spindly tips of the bare trees, and they stand out in clear silhouette against the last light of the day. But I cannot name them. The first rule of identifying bats is that doing so reliably from any distance is near impossible. You practically have to hold them to know their species for certain. If I had to guess I would guess that these bats are pipistrelles, Britain’s most common. But I don’t, and so they remain simply bats.

With every movement the bats emit high frequency squeaks beyond the hearing range of most adult humans. Children can often hear these calls, but as we age our frequency range narrows until bats appear entirely soundless. I can still, just about, make them out, calling out insistently like unoiled hinges. It is a sound to be appreciated, as it is likely to be lost to me within five years, and the sound of an experience entirely unknowable.

These sounds provide the bats with a comprehensive knowledge of their dim surroundings. Microchiroptera like these navigate their twilight world primarily through echolocation, their constant high-pitched sounds bouncing from every surface back to specialised ears which then create a highly detailed map of their surroundings. It is the same principle as sonar, and sophisticated enough to allow them to pinpoint the exact trajectories of insects measuring just a couple of millimetres. The bats which fly around me, inches from my face, are experiencing the world in a way I am not equipped to imagine. They can hear what I can see; the trees waving in the breeze, the pigeons curled up in the branches, the cold metal railing of the balcony. They can hear the camera in my hands and the grooves and features of my face.

American philosopher Thomas Nagel saw in this alien ability the limitations of purely physical understandings of the universe. The relationship between worlds physical and mental – between the brain and the mind – is one of the most fundamental problems of Western philosophy. In the late twentieth century, following two hundred years of scientific rationalism, the default position in academic circles was that there was nothing ‘mystical’ about consciousness; our minds could, with sufficient insight and complexity, be explained purely in terms of the physical operations of our brains.

In his cryptic 1974 essay What is it Like to Be a Bat? Nagel presents a problem for this sort of physical reductionism by asking to what extent a bat’s experience of the world is accessible to us. As conscious beings, aware of the world in which they live, there is, as Nagel puts it, ‘something it is like to be a bat’. But much of that phenomenological experience is based upon sonar, a sense for which we have no parallel. Try to imagine a mental map of your surroundings constructed from sound. It is impossible. The closest we can come is a sort of image made from sound, a poor translation of an auditory experience into something more familiar to us. Even that word imagination, the process by which we transport ourselves into different modes of being, hints at our dependence on sight in our mental recreations of the world, and how distant a bat’s experience is from our own.

For Nagel, however, the kernel of consciousness is that interaction between a mind and its world – that ‘something it is like to be’. The gulf between bats’ experience of the world and our own highlights how ‘the facts of experience… are accessible only from one point of view’, and how we are entirely unable to adopt the point of view of a bat. No amount of physical study, of bat neurophysiology or high frequency acoustics, could communicate to us what it is like to be a bat experiencing the world through its innate faculty of echolocation. Nagel’s idea of the irreducible, constitutive element of experience is now known as the subjective dimension of consciousness and his paper, nearly fifty years after publication, continues to divide and dictate philosophies of mind.

A particularly bold stoop, almost striking my face, brings me back into my own subjective dimension. As the bats dance around me, I am struck not so much by the gulf between us, but by our proximity. Whatever the superficial differences, the bats and I, along with the pigeons and the trees they sit in, and the unfortunate insects being eaten in their hundreds, all share in a fundamental experience of existence. One also irreducible, but unifying across all creatures. I stand and share it with the bats for a while longer until, just as they arrived, they disappear, slipping out of existence into the now complete darkness of the night.