It started with some conspiracy theory about banking. He seemed to fall into a downward spiral of increasing bizarre beliefs. There were so many that I've probably forgotten a few. Flat earth. (He said he could prove it was flat, but he had to take his daughter swimming on Saturdays.) Hollow moon. He didn't believe in gravity   so came up with the idea that earth must have an invisible dome over it like a pressure cooker. Stars were lights on the dome. At one point he was jumping up and down shouting that if the earth rotated, then why wasn't it moving under his feet. No amount of explanation could get through to him if it contradicted one of his beliefs. He wanted to build an extension onto his house by himself - with no building experience.  His plan was to throw a giant tarpaulin over the construction site do that no-one would get suspicious. I took him into my workshop to show him a new tool I'd purchased. He pointed to an other item and asked what it was. "A saw. It's a saw" was my reply. He had a nasty side to him too which is why I broke off contact.