Tesla used to experience visual hallucinations. Any time an object was mentioned in conversation it would appear before him as if it where real. He started getting these hallucinations randomly and began to obsess about their origins. Over time he was able to trace the source of every hallucination to something which he had heard or seen earlier. He then noticed that the same was true for all of his thoughts, every one could be traced to some external stimuli. From this he concluded that he was an automata controlled by remote input. This inspired him to invent the first remote control vehicle.