solipsist

This term carries a heavy philosophical weight, often evoking a sense of profound isolation or intellectual arrogance. While it describes a specific epistemological position, in common parlance it is frequently used as a pejorative to describe someone who is excessively self-absorbed or unable to recognize the validity of other people's experiences.

As a noun, it refers to the individual adhering to the doctrine. As an adjective, it describes the nature of the belief system or the mindset itself. The word implies a total collapse of the boundary between the internal mind and the external universe, suggesting that reality is a private construction.