“The Brain – is wider than the Sky – / For – put them side by side – / The one the other will contain / with ease – and You – beside –,” wrote Emily Dickinson. To all that the world presents to our senses, the mind effortlessly adds things that will not and cannot ever be. We can’t help it: imagination is humankind’s unbidden superpower, perhaps the capacity that most distinguishes us from other animals.

In The Shape of Things Unseen, neurologist Adam Zeman attempts to explain how and why this is. It is a wide-ranging survey – too wide, offering a mass of fascinating information about creativity, mental imagery and child development bloated by superfluous discourses on the origins of life, the Covid pandemic and climate crisis. Even then it doesn’t quite resolve the mystery of why our imaginative capacity seems to far exceed what is adaptively useful. But in this Zeman simply reflects the state of play: brain science tells us a great deal about the imagination but can only ever take us so far.

The subject itself is multivalent. How much common ground should we expect between the visionary William Blake (for whom “this world is all one continued vision of fancy or imagination”) and physicist Paul Dirac, who apparently struggled to imagine himself into the mind of others and yet was able to dream up antimatter and single-pole magnets? Imagination seems clearly linked to creativity, empathy and the ability to conjure up mental images, yet some highly creative people, such as Pixar’s founder Ed Catmull, are “aphantasic”, innately unable to visualise anything in the mind’s eye.

Imagination of a sort is central to all experience. “Perception and imagination occupy more common ground than we tend to suppose,” Zeman writes. We construct our perceived world from incomplete information, interpreted via inner representations of our environment, that generate predictions of what is actually out there and how it will respond to our actions. “[Mental] imagery exists to enable us to make more accurate predictions of future events in the interests of effective behaviour,” he says. “It does so by allowing us to simulate those events in somewhat lifelike ways.” The distinction between the imagined and the real is then blurry: imagined exercise can increase strength, imagined drugs might facilitate cure, imagined pain is still pain.

Our reality is thus what some scientists have called a controlled hallucination: an imagined world more or less correlated with the physical one but apt to lose that correspondence when the associated brain functions are dysregulated by drugs or illness.

Zeman might have found it easier to organise his unruly material around a concept we can call “imaginality” – not imagination per se but the cognitive attributes needed for it, just as we might distinguish the acts of making and hearing music from musicality, the faculties we bring to bear for those tasks. The notion of imaginality clarifies how we differ from and resemble other animals. For us it seems a profoundly and uniquely social attribute. Humans have a strong “theory of mind”: we typically act on the assumption that others have minds like ours, with their own set of goals and experiences. Other animals show signs of this – some birds, say, hide food in a way that suggests a perception of what others might know and do. But no other creature seems as socially oriented. Young infants are no more physically adept at many tasks than chimps or orangutans, yet they instinctively seek and expect cooperative behaviour from others. “The human condition is one of incessant mind-sharing,” Zeman writes. “When we blush, whether with pride, shame or embarrassment – as only humans do – we are expressing our uniquely human awareness of where we stand in others’ minds.”

Social imagination perhaps holds the key to the most striking distinction between us and other animals: language. As with many human traits, it’s easy to think up – because we are imaginative – stories to “explain” the adaptive value, in Darwin’s sense, of being able to communicate complex ideas and instructions. But some researchers think language arose less for immediate utilitarian ends, but rather to enable us to project an inner world from one individual to another: in effect, to tell stories. In this view (sadly not really explored in any depth here), language is an inherently creative cognitive tool, not just used to coordinate social activity but engendering the Icelandic sagas, The Waste Land, The Archers.

But while The Shape of Things Unseen is good (if a little disorganised) on the science, it is rather pedestrian on cultural aspects of imagination. “For TS Eliot, in the 1920s, the problem was how to convey his sense of personal and social disintegration in the wake of the first world war: familiar poetic forms seemed to fall short of the aim.” And with his rules for creativity, Zeman seems to be pitching at the motivational business market. There is a thought-provoking shorter book that could have been assembled with some judicious pruning and reorganisation. That might have better conveyed the important message that imagination is not what an artistic elite uses but a universal capacity, essential also to science (“Imagination is the discovering faculty [that] penetrates into the unseen worlds around us, the worlds of science,” wrote Ada Lovelace), as indeed it is to the human condition.