I think he is saying that if our true state is some kind of infinite conciousness or soul, then our existence while incarnate on this earth is some
kind of deception whereby we are made to forget our true nature.
I think he's also saying that we are the cause of the deception ('father of lies').
If this is the case I like to think of our existence being akin to a video game or watching a movie. When you watch a movie you become absorbed by it
and also suspend your disbelief. You don't spend the whole time thinking to yourself that what you're watching is just a film, the people in it
only actors etc. Only once the movie is finished do you remember who you are.
It may be that Life is similar and is either a form of entertainment or education (or edutainment

) for our souls.