"Unshakeable belief" refers to having a strong and unwavering trust or confidence in something, to the point that it cannot be easily swayed or doubted. Full definition
I also had to learn to keep my new found unshakeable belief in God and how that happened to myself. (nakedpastor.com)
And Davison claims that he got the same sense of unshakeable belief from all the players he spoke to, with Kieran Gibbs suggesting that the transfer of Petr Cech from Chelsea has had a really big effect. (justarsenal.com)
Psychosis is a term used to indicate mental health disorders that present with symptoms like hallucinations (such as hearing voices) or delusions (unshakeable beliefs based on the person's altered perception of reality, which may not correspond to the way others see the world). (kcl.ac.uk)