“Reality is merely an illusion, albeit a very persistent one.” – Einstein
“‘Philosophy and Predictive Processing’ focuses entirely on the influential theory in its title, which argues that our brains are constantly making predictions about what’s out there (a flower, a tiger, a person) and these predictions are what we perceive.
To make more accurate predictions, our brains modify their internal models of the world or force our bodies to move, so that the external environment comes in line with predictions. This idea unifies perception, action and cognition into a single framework.
Some of the titles of the papers are playful, and maybe a tad over-the-top: ‘How to entrain your evil demon’, ‘How to knit your own Markov blanket’ or ‘Of Bayes and Bullets’. But despite the titles, the content is serious and heavy-going: it’s written by some well-known proponents of predictive processing, including Andy Clark, based at the University of Edinburgh, UK, and Jakob Hohwy, at Monash University, Australia.”
A guide to why your world is a hallucination – New Scientist
the observer effect 
I don’t get it. On one hand you say that reality is a illusion (a statement with which I wholeheartedly agree) Then you describe a process that performed by the brain. Really? An illusion is performing a function like rational thought? Come on now. This makes no sense.
It’s the equivalent of me saying: my teddybear is only a stuffed animal, it contains no creative or cognitive ability whatsoever. He is not sentient. I know this because he told me so.
I said nothing. The headline quote is a misattribution to Einstein (I was having some fun), and the body text is an excerpt from the linked article on predictive processing theory, which involves the brain.