What Symptoms Indicate The Presence Of Schizophrenia?

My 21 year old son has been have conversations people that don t exist - believes that he sees the future. Has false memories of the past. I believe he has has the beginnings of schizophrenia. He believes he isn t going crazy and that we will all see soon. It will all come clear. Because he doesn t believe he has a problem how can I convince him to see a doctor?