You might think of it like this: DID: Alice is talking to Bob. At some point in the conversation Bob "dissociates" and is replaced by Charlie. Charlie is in th

You might think of it like this: DID: Alice is talking to Bob. At some point in the conversation Bob "dissociates" and is replaced by Charlie. Charlie is in the exact same place as Bob and sees all the things Bob was seeing, but Charlie wasn't here before so no idea where here is, how he got there, or who is talking to him. Alice doesn't know anything's wrong at first but Bob (now Charlie) seems uncomfortable and doesn't know things Bob does, like where they are, how they got there, or who she is. Sometime later the dissociative episode ends and Bob comes back in place of Charlie. Bob has no idea what transpired during the episode because Charlie was there instead, but recognizes Alice and remembers things they had done together. In this case there is no difference in Bob's or Charlie's ability to perceive the world, nor are either of them perceiving something which Alice could not (barring other conditions). There are no hallucinations or delusions; Bob and Charlie appear to "know" different things, as if they were different people. Of note, Bob and Charlie identify differently but its debatable whether they are (or should be treated as) different persons, hence the change of name. Schizophrenia: Alice is talking to Bob. Bob is talking to Charlie. Charlie isn't really there, but Bob is either unaware or doesn't mind. Bob's conversation with Charlie may be benign or it may involve plots to take over the world, in either case from Alice's perspective Bob experiencing something which isn't real. This of course is just a possible scenario for schizophrenia, and if Bob is being treated for schizophrenia he may be better able to control or cope with Charlie. In schizophrenia cases Charlie does not exist to any third party observation; Bob is not identifying as Charlie nor is Charlie an alternate persona. Bob believes he is himself and that Charlie is communicating with him.