I usually don’t like it when people use unnecessary big words. But sometimes a word comes by that explains exactly the idea. One of my favorites is Schadenfreude ( it’s funny and real at the same time). When I noticed the author used Solipsism, I definitely judged him for a moment, but after I read the explanation, it was a beautiful description of his stance :)

Solipsism is a philosophical position asserting that only one's own mind is certain to exist.