Over an external source? Hallucination would only affect you, not the outside world. So either you are grasping for insanity, or are in denial. Further evidence is that I exist outside of your computational power. I think and process and type things that are entirely impossible for you to predict, whereas hallucinations are YOUR mind expressing divergent thoughts in an understandable manner- like dreams you would be able to predict what happens next. You in essence would be in control.