A 1991 book by American philosopher Daniel Dennett, which offers a comprehensive theory of consciousness. Dennett argues that consciousness is not a mysterious, non-physical phenomenon but rather a product of complex brain activity, challenging traditional dualistic views.
That's why Daniel Dennett said consciousness is an illusion.
""Daniel Dennett was mentioned by name in the context of his views on consciousness, specifically that 'consciousness is an illusion' because he 'couldn't do anything with it' from a Darwinian perspective. This book is his seminal work on the topic."