But it could just be I that exists. Or the other way around. In which case the other does not "exist". Responses and words are poor examples. They are perhaps the easiest of all things for out brains to produce. So if I talk to myself, does that mean that there is someone really existent answering me? You can I both know the answer. We can flit around the truth all we want, but we know the answer is and always will be no. Why? Because one intelligence can not exist as two separate entities, each with independent thoughts and emotions.