The phrase "pure delusion" means having thoughts or beliefs that are completely false or imaginary, with no connection to reality. It describes a state of extreme misconception or fantasy. Full definition
Many parents also imagine (and this is pure delusion in almost every case) that their young person will be capable and solely responsible for an animal's care. (petbusiness.com)
The other effect of zero interest rate policy is pure delusion. (hussmanfunds.com)