Though Scripture doesn't suggest they can read our minds or know the future, demons are certainly aware of much truth we aren't. Their modus operandi is to twist, deceive, and mislead, but they are intimately familiar with the truth they twist. In fact, they may even quote Scripture in their attempts to mislead us, as Satan did in his temptation of Christ. Demons see spiritual realities they have no choice but to believe, no matter how much they rebel against them. They hate the incarnation, virgin birth, and resurrection, but they believe them with as much conviction as the most fervent Christian.
Demons are atheists in their behavior, but fundamentalists in their beliefs.
Despite this, though, I suspect their finite minds and twisted natures keep them from understanding or fully believing lofty realities such as the love and grace of God. This surfaces in some of Foulgrin's letters. I also believe demons are capable of self-deception, which partly explains their initial rebellion. This accounts for my portrayal of Foulgrin as sometimes imagining his side can win the war and reclaim heaven, and other times despairing because he realizes his inevitable destiny is hell. The purpose behind Lord Foulgrin's Letters is simple.