Solipsism
I just had a word pop into my head during dinner: solipsism.
I couldn’t remember what it was, so I looked it up.
This is from Wikipedia, like most things these days:
The word solipsism (Latin: solus, alone + ipse, self) is used for two
related yet distinct concepts:
* An epistemological position that one’s own perceptions are the
only things that can be known with certainty. The nature of the
external world — that is, the source of one’s perceptions — therefore
cannot be conclusively known; it may not even exist. This is also
called external world skepticism.
* A metaphysical belief that the universe is entirely the
creation of one’s own mind. Thus, in a sense, the belief that nothing
‘exists’ outside of one’s own mind.
That is kind of spooky.