The phrase "such illusions" refers to false beliefs or misleading perceptions. It means that there are misconceptions or ideas that are not based on reality. Full definition
I adore the look of camel and brown together it gives such a illusion of warmth. (lovely-pepa.com)
I guess if some want to pretend there is no difference in our beliefs then fine... but I don't see how such an illusion will help either of us in our journey. (nakedpastor.com)
Hmmm... if they just took that one more step, they might consider asking what kind of God would create such an illusion, and then they might actually stretch their brains abit more and ask, «What kind of God would be willing to lie like that?» (religion.blogs.cnn.com)