More than meets the eye

i) A trope we find in some scifi and horror flicks is vampires, werewolves, and extraterrestrials who can pass for humans. Except when they transform on a full moon, werewolves are indistinguishable from humans. Vampires have no vital signs, but they look human on the outside, even if they work the graveyard shift. Alien invaders transfer their minds to human bodies to use as vehicles. 

So these beings blend into the human population undetected. Humans see what's on the outside, but they can't discern what's on the inside. 

When, however, a werewolf meet another werewolf, they instantly recognize each other. Werewolves, vampires, and aliens can sense one of their own kind. 

In the Gospels, demons instantly recognize the underlying identity of Jesus (e.g. Mk 1:23-25,34; 3:11; 5:7). Although Jesus is human, he's more than human. But his deity is not an empirical property. Some of his actions signify his deity, but it can't be physically sensed.

Yet when demons encounter him, there's instant recognition since fallen angels and the Son of God all hail from the spiritual realm.  

ii) And this indicates why, in these passages, "Son of God" can't be merely legal, in the sense that David was God's adoptive son, and Jesus is the heir of David, for there's nothing about a legal status that's discernible or observable. A legal status is ascriptive. There's no evidence just from encountering the individual. 

Instead, the demons pick up on something deeper. Intangible. Something on a different wavelength entirely. The presence of their Creator Incarnate. And it's very threatening to them. Analogous to humans who experience theophanies. 

Angels are telepaths. Minds coming into contact with other minds. They have direct awareness of who Jesus is. 

As Lee Irons put it, not merely a “son of David kind of Messiah” but a “Son of God kind of Messiah.”