If the delusions are benign, go along with them and redirect attention to something else. For example, if his delusion is that the mailman is going to bring something wonderful, you can say, "Well, won't that be great! You deserve it. The mailman won't be here for a few hours, so let's go for a walk now." If the delusions are frightening or distressing to the person, don't try to convince him they are not real -- that simply will not work -- but do what you can to reassure him. If he is sure there are police outside to arrest him, try something like, "Oh, I forgot to tell you! The city has stepped up its neighborhood patrol because of some vandalism. If you see police, it has nothing to do with you. There is no cause for you to be arrested."
If a person has delusions that there is a problem, it is not usually possible to convince him that the problem doesn't exist. It is often easier to reassure him that you are taking care of the problem, that the problem will be over soon, that you are getting someone to fix it first thing in the morning, etc.
I really like this true story from another discussion board: The husband, with dementia, couldn't sleep and was fretting that there was a fish hook in his blanket. His wife was more creative than most of can be at 3:30 am. She told him she would get a pliers and get it out. While she was gone she also palmed a fishing lure. She came back into the bedroom, worked with pliers for a few moments, exclaimed, "Ah, ha, I got it!" and showed him the fish lure. They both got to sleep the rest of the night.
Remember that the point is provide comfort and reassurance to the person having the delusion. It is not to "teach" them something, or to convince them of the "truth."
His brain is creating all these strange ideas. In a way, pretend for a minute that what he is saying is true, and answer as if it is true. You will need to be creative.
If a person has delusions that there is a problem, it is not usually possible to convince him that the problem doesn't exist. It is often easier to reassure him that you are taking care of the problem, that the problem will be over soon, that you are getting someone to fix it first thing in the morning, etc.
I really like this true story from another discussion board: The husband, with dementia, couldn't sleep and was fretting that there was a fish hook in his blanket. His wife was more creative than most of can be at 3:30 am. She told him she would get a pliers and get it out. While she was gone she also palmed a fishing lure. She came back into the bedroom, worked with pliers for a few moments, exclaimed, "Ah, ha, I got it!" and showed him the fish lure. They both got to sleep the rest of the night.
Remember that the point is provide comfort and reassurance to the person having the delusion. It is not to "teach" them something, or to convince them of the "truth."
Good luck.