Building a complex theory on an absence is a brave enterprise, even for a neuropsychiatrist specialising in epilepsy. However, for Michael Trimble, the crucial absence is a statistical one: that among the many people suffering from epilepsy there are remarkably few poets. From that negative association, along with a similar absence of poets with schizophrenia and an overabundance of writers with bipolar disorder, and using a careful linguistic analysis of psychopathology, Trimble's ‘central aim… is to relate… religion, poetry and music to their underlying neurological basis’. Indeed, it is an attempt to describe the soul of man, those uniquely human features which together provide a sense of existence, of purpose, of being in the world and of it. And, ‘the thread that unites them [all]… is the neurobiology of the non-dominant hemisphere’.

Trimble suggests that although neurology has carefully dissected the left-hemisphere lesions causing the aphasias, the right hemisphere's contribution to the mood, feeling, rhythm and consonance that underpin poetic language is relatively neglected. This, though, is not yet another ‘simple right-brain left-brain dichotomy’, for, as Trimble rightly says, normally the hemispheres cooperate, their separate functions only manifesting in the clinic. Nevertheless, Trimble does quote Nietzsche's suggestion of ‘two chambers of the brain… one to experience science and the other non-science’; and science has not done well at thinking about art, music and religion.

The book's central argument is neuroanatomical and evolutionary, splicing cerebral asymmetry onto MacLean's triune brain, so that ‘links from the limbic structures to the right hemisphere may have remained or developed to a greater degree than those to the left hemisphere’. From here, one journeys through religious belief to ‘the physicality of listening to music, poetry, and religious incantation, and the shivers down the spine [that] are often associated with tears’. The book's heart is its two chapters on neurotheology, the author treading carefully in a field with ‘few hard and fast data… and [where] most writers… recycle the same results from a small number of investigators’.

This scholarly, yet provocative, book from an insightful, observant neurologist, perhaps inevitably written more using the linguistic precision of the left hemisphere than the poetry of the right, is rich with thought-provoking ideas on the unique human characteristics that Trimble calls the ‘seven L's’ – Language, Laudation, Lying, Laughter, Lachrymation, Lyric and Love – each, as he says, ‘quintessentially driven by the right hemisphere’.