Patient not accepting his illness.

How to help psychiatric patient when he is not accepting his illness? My father don't accept that he has any mental illness, we tried everything he says he is going to work daily he is fine. But he has all symptoms schizophrenia. When he was at age 27 he took schizophrenia treatment for almost 2 year after he was fine but from last 5-6 year all symptoms come back. When we told him that he took treatment in past he says 'doctors made fool of him that time he never had any illness'. How can we get him to doctor when he is not even accepting that he has schizophrenia. Symptoms- he think everyone around us planning against our family, he make fake negative stories, he says neighbours say negative words when he pass by (not true), he don't have any friends anymore, gets angry easily, anxious all time, think he is superior than everyone around him etc. How can we help him he don't listen to anyone. Please help