Have you ever used the word 'Solipsistic' in a sentence before?

Solipsism is the philosophical idea that only one's mind is sure to exist. As an epistemological position, solipsism holds that knowledge of anything outside one's own mind is unsure; the external world and other minds cannot be known and might not exist outside the mind.

Who knew there was a term for what us Aussies would say 'having your head stuck up your own ass'