Solipsism
Etymology
From Latin "solus," "alone," plus "ipse," "self" — literally “self-alone.” The term emerged in the 1700s to name the extreme conclusion of taking radical doubt seriously: if all you truly access is your own experience, everything beyond it becomes an unprovable assumption.
noun · /SOL-ip-siz-um/
The view that the only thing one can be sure exists is one’s own mind — everything else may be doubtful or unreal.
What it names
A handle for the isolating thought experiment at the edge of skepticism: how could you ever prove that other minds, or the outside world, exist at all?
Example
Scrolling through accounts that all seemed to confirm his views, he felt a creeping solipsism, as if the whole feed were staged for him alone.
Related idea
Skepticism questions whether we can know things for certain; solipsism is its most radical endpoint, doubting that anything beyond one’s own mind exists to be known.