What If Reality and Imagination Are the Same System?

We usually treat perception as contact with the external world and imagination as a private mental exercise, but neuroscience suggests the boundary between them is thinner than it first appears. Modern work on visual mental imagery shows that imagination recruits brain systems that overlap substantially with those used in perception, memory, and planning.

Older models often treated perception as passive reception, as if the brain simply recorded incoming sensory data. That view has long been challenged, and Held argued that perception is better understood as an active process rather than a passive one. 

Pearson’s review similarly describes visual imagery as involving a distributed network spanning frontal and sensory regions, with overlap in systems linked to the default mode network, and notes that imagery can function like a weak form of perception. In other words, both seeing and imagining depend on the brain’s constructive activity, even though they differ in how strongly they are constrained by sensory input.

Research on imagination also shows clear links to memory. Schacter, Benoit, and Szpunar define episodic future thinking as the capacity to imagine or simulate experiences that may occur in one’s personal future, and they show that it draws on mechanisms shared with episodic memory. 

Pearson’s review likewise emphasizes that mental imagery is closely related to memory recall and other cognitive functions. This means imagination is not just free-floating fantasy; it is often built from stored experience, recombined into new scenarios.

The hippocampus appears central to this constructive process. Recent models describe the hippocampus as supporting memory construction, reconstruction, and generative scene building rather than acting only as a passive storehouse. Jensen, Hennequin, and Mattar show that planning can be modeled as sampling imagined action sequences, with hippocampal replay-like patterns emerging in a recurrent network framework. 

Taken together, these studies support the idea that memory, imagination, and planning rely on overlapping neural machinery for constructing possible scenes and actions.

The same overlap helps explain why imagined practice can affect performance. If planning and imagery activate systems involved in action selection and simulation, then mentally rehearsing a task can shape later behavior, at least in principle. 

Likewise, the vividness of imagery varies across individuals, and Pearson notes a spectrum ranging from aphantasia to highly vivid imagery. That variability matters because it shows that imagination is a measurable cognitive capacity, not merely a vague introspective label.

This neuroscientific picture does not prove the universe is a simulation. Bostrom’s argument is a philosophical proposal about the statistical possibility that advanced civilizations could run ancestor simulations; it is not a claim established by neuroscience. 

What neuroscience does support is a more modest but still striking point: the brain itself constructs experience through predictive and generative processes, so our lived reality is already partly simulated from within. Perception, memory, future thinking, and imagination are therefore better understood as related modes of internal construction than as fully separate mental systems.

Seen this way, imagination is not the opposite of reality. It is one of the brain’s ways of testing possibilities, integrating memory, and preparing for action under uncertainty. Reality is the version of that process most tightly constrained by sensory evidence and shared conditions; imagination is the version with looser constraints and greater room for recombination. The distinction remains real, but it is a difference of degree, not a hard divide 

References 

Bostrom, N. (2003) Are We Living in a Computer Simulation? The Philosophical Quarterly, 53, 243-255.

https://doi.org/10.1111/1467-9213.00309

Pearson, J. (2019). The human imagination: the cognitive neuroscience of visual mental imagery. Nature Reviews Neuroscience*, 20(11), 624–634. https://doi.org/10.1038/s41583-019-0202-9

Schacter, D. L., Benoit, R. G., & Szpunar, K. K. (2017). Episodic future thinking: mechanisms and functions. Current Opinion in Behavioral Sciences, 17, 41–50. https://doi.org/10.1016/j.cobeha.2017.06.003

Jensen, K. T., Hennequin, G., & Mattar, M. G. (2024). A recurrent network model of planning explains hippocampal replay and human behavior. Nature Neuroscience, 27(7), 1340–1348. https://doi.org/10.1038/s41593-024-01675-7

Spens, E., & Burgess, N. (2024). A generative model of memory construction in the hippocampus. Nature Human Behaviour, 8, 546–561. https://doi.org/10.1038/s41562-023-01799-z

Zacks, O., & Jablonka, E. (2026). The neural basis of imagination: An evolutionary and computational perspective. Trends in Cognitive Sciences. https://doi.org/10.1016/j.tics.2026.01.004

Held, R. (1989). Perception and its neuronal mechanisms. Cognition, 33(1–2), 139–154. https://doi.org/10.1016/0010-0277(89)90008-5

Kumar, P. (2026, April 11). The Scientific Explanation of Perception: A Cognitive Perspective • Philosophy Institute. Philosophy Institute. https://philosophy.institute/philosophy-of-mind/scientific-explanation-perception-cognitive-perspective/