In this 1977 video, surrealist science fiction author Philip K. Dick suggests we are living in a computer simulation.
We are living in a computer-programmed reality, and the only clue we have to it is when some variable is changed, and some alteration in our reality occurs. We would have the overwhelming impression that we were re-living the present – déjà vu – perhaps in precisely the same way: hearing the same words, saying the same words. I submit that these impressions are valid and significant, and I will even say this: such an impression is a clue, that in some past time-point, a variable was changed – re-programmed as it were – and that because of this, an alternative world branched off.
"The Origin of 'A Glitch in the Matrix': Philip K. Dick Discusses Déjà Vu and Living in a Simulation, in 1977" (Daily Grail)
