Solipsism (/ˈsɒlᵻpsɪzəm/; from Latin solus, meaning 'alone', and ipse, meaning 'self') is the philosophical idea that only one's own 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. As a metaphysical position, solipsism goes further to the conclusion that the world and other minds do not exist.

https://en.wikipedia.org/wiki/Solipsism

Morpheus: What is real? How do you define 'real'? If you're talking about what you can feel, what you can smell, what you can taste and see, then 'real' is simply electrical signals interpreted by your brain.

Philip K. Dick: Reality is that which, when you stop believing in it, doesn’t go away. [...] I think that, like in my writing, reality is always a soap bubble, Silly Putty thing anyway. In the universe people are in, people put their hands through the walls, and it turns out they're living in another century entirely. … I often have the feeling — and it does show up in my books — that this is all just a stage.

A psychologist said, “They used to talk about seeing only ‘reflections’ of reality. Not reality itself. The main thing wrong with a reflection is not that it isn’t real, but that it’s reversed.”

The basic tool for the manipulation of reality is the manipulation of words. If you can control the meaning of words, you can control the people who must use the words.