If it is never your experience that a thought exists outside of consciousness, then it makes no sense to carry around the notion that it really does exist externally. And because memory is itself another thought, it can’t prove the existence of another thought even within consciousness. One realizes that there’s no evidence that a thought existed other than the present thought. There cannot be two thoughts. If there can’t be two, then it makes no sense that the present thought is actually a thought in the first place. At this point, thought itself dissolves into consciousness. Even the most subtle separation and movement and sense of existence/non-existence dissolved into the sweet, loving arms of pure consciousness.
Pure consciousness is called the "I-Principle." It is that to which everything appears. It is your very self.
http://www.heartofnow.com/files/atmananda.html#outside.in