The concept of free couldn't arise within beings devoid of free will in the first place. Free will cannot be an illusion, because an illusion is a false representation of something that already exists. If it's an illusion, what is it an illusion of? The materialist will say "Free will is the illusion of feeling able to make real choices." In other words: free will is the illusion of free will? Meaningless. The concept of free will proves its own existence, regardless of any interpretations of scientific data pro or against.