Although Proof of Heaven became a bestseller, its central claims faced significant challenges from the journalistic and scientific communities. The book engages with the “hard problem” of consciousness (the challenge of explaining subjective experience through objective science). Some researchers confront this challenge via neurophenomenology, which formally integrates first-person reports into neuroscientific inquiry. Biologist Francisco J. Varela, a leading voice in neurophenomenology, defined it as “a quest to marry modern cognitive science and a disciplined approach to human experience” (Varela, Francisco J. “Neurophenomenology: A Methodological Remedy for the Hard Problem.” Journal of Consciousness Studies, 1996). Neurophenomenology has found use in clinical studies of near-death experiences (NDEs) in cardiac-arrest survivors, whose detailed reports are not easily explained by purely physiological factors.

Alexander adopted the neurophenomenology approach, treating his coma experience as a rigorous “N-of-1” (92) case study. Following his son’s advice, he documented his memories before consulting external literature. His account, which includes phenomenological aspects (like a feeling of hyperreality, direct acquisition of nonverbal knowledge, and iterative transitions between distinct realms), relies on his claim that consciousness persisted despite cortical inactivity due to severe bacterial meningitis.

Thus, the book’s credibility rests on Alexander’s assertion that his NDE occurred while his neocortex was completely nonfunctional. However, a 2013 investigative article in Esquire magazine by Luke Dittrich contested this claim: “Before Proof of Heaven made Dr. Eben Alexander rich and famous as a ‘man of science’ who’d experienced the afterlife, he was […] a neurosurgeon with a troubled history and […] in need of reinvention” (Dittrich, Luke. “The Prophet.” Esquire, 2013). Citing medical records and interviews, Dittrich reported that Alexander’s doctors had placed him in a medically induced coma and that he experienced periods of consciousness with delirium, suggesting that his brain was not entirely offline, as the book claims.

In a 2013 article in Scientific American, Michael Shermer asserts that Alexander’s experience is proof of hallucination rather than heaven. During Alexander’s appearance on Larry King’s live streaming talk show on Hulu, Shermer, convinced of Alexander’s genuine belief that he experienced heaven, submitted a question via the show’s virtual Green Room:

I asked him how, if his brain was really nonfunctional, he could have any memory of these experiences, given that memories are a product of neural activity? He responded that he believes the mind can exist separately from the brain. How, where, I inquired? That we don’t know yet, he rejoined. The fact that mind and consciousness are not fully explained by natural forces, however, is not proof of heaven (Shermer, Michael. “Why a Near-Death Experience Isn’t Proof of Heaven.” Scientific American, 2013).

Neurologists Sam Harris and Oliver Sacks likewise questioned Alexander’s conclusions, arguing that such a vivid experience was unlikely to have happened during a state of cortical inactivity. They proposed clinical explanations, such as hallucinations produced under extreme stress or a “reboot phenomenon,” wherein the cortex constructed complex memories as it returned to function (Harris, Sam. “This Must Be Heaven.” Sam Harris Blog, 2012). Alexander publicly defended his account, stating that critics distorted the facts (Alexander, Eben. “The Science of Heaven.” Newsweek, 2012).