Why is self an illusion?
Gnōthi seauton (γνῶθι σεαυτόν), know thyself.
But what is self? And why call it an illusion? Perhaps because you are, most literally, the continuation of everything that ever was, and the precursor to everything as it will be — the very limited delusion of ego and selfish desire fail to full capture, even in clever metaphor, the totality of existence.
How is a mind to abstract infinite silence? Thought, knowledge, and the very process of a mind cannot capture and constrain that which is beyond itself– beautiful as the illusions may be, there is freedom beyond the constraints of ego and selfish desire.