Our desire for entertaining virtual realities is increasing. As our understanding of the human brain also accelerates, we will create both imagined realities and a set of memories to support these simulacrums. For example, someday it will be possible to simulate your visit to the Middle Ages and, to make the experience realistic, we may wish to ensure that you believe yourself to actually be in the Middle Ages. False memories may be implanted, temporarily overriding your real memories. This should be easy to do in the future — given that we can already coax the mind to create richly detailed virtual worlds filled with ornate palaces and strange beings through the use of the drug DMT (dimethyltryptamine). In other words, the brains of people who take DMT appear to access a treasure chest of images and experience that typically include jeweled cities and temples, angelic beings, feline shapes, serpents, and shiny metals. When we understand the brain better, we will be able to safely generate more controlled visions.
Our brains are also capable of simulating complex worlds when we dream. For example, after I watched a movie about people on a coastal town during the time of the Renaissance, I was “transported” there later that night while in a dream. The mental simulation of the Renaissance did not have to be perfect, and I'm sure that there were myriad flaws. However, during that dream I believed I was in the Renaissance.
If we understood the nature of how the mind induces the conviction of reality, even when strange, nonphysical events happen in the dreams, we could use this knowledge to ensure that your simulated trip to the Middle Ages seemed utterly real, even if the simulation was imperfect. It will be easy to create seemingly realistic virtual realities because we don't have to be perfect or even good with respect to the accuracy of our simulations in order to make them seem real. After all, our nightly dreams usually seem quite real even if upon awakening we realize that logical or structural inconsistencies existed in the dream.
In the future, for each of your own real lives, you will personally create ten simulated lives. Your day job is a computer programmer for IBM. However, after work, you'll be a knight with shining armor in the Middle Ages, attending lavish banquets, and smiling at wandering minstrels and beautiful princesses. The next night, you'll be in the Renaissance, living in your home on the Amalfi coast of Italy, enjoying a dinner of plover, pigeon, and heron.
If this ratio of one real life to ten simulated lives turned out to be representative of human experience, this means that right now, you only have a one in ten chance of being alive on the actual date of today.