Conventionally, people’s ability to distinguish between reality and non-reality is strongly linked with their mental soundness.

When we are young, these boundaries are not so well-defined. Children often have imaginary playmates. Some of those playmates may even have fixed identities and features. It is also quite common for children to experience vivid dreams and nightmares. When we grow up, as a result of parental and social conditioning, we begin to partition the world into three main areas: Reality, Imagination, and Dreams. We still experience all the three areas, but maintain strict differentiation. For example, J.K. Rowling may be celebrated for her “Harry Potter” fantasy series, but if she suggests believing in any part of her imagination as real, society would label her as delusional. Imagination is easier to determine though, because imagined experiences are less vivid—one cannot feel physical pain just by imagining being run over by a truck. Dreams are more complicated, because all our senses of vision, hearing, smell, touch and taste might be involved. On what basis then do we draw a clear line between dreams and reality?

I think that our belief that an experience is ‘real’ is reinforced by consistency along two dimensions:

  • Feedback Consistency: If other people confirm what we experience.
  • Temporal Consistency: Repeated experiences over time with the same actors and objects.

When there is a conflict between the two, feedback consistency often takes precedence. If we draw circles around people’s heads representing their perceived realities, then we may get a ‘collective reality’ corresponding to the area with the highest overlap.

Now consider the possiblity that this collective reality might just be a figment of the imagination of an alien in another galaxy. Alternatively, it might just be a bubble in the head of someone committed to a mental institution for digressing from our established rules of ‘reality’.