2:19

the demons believe: With this statement, James argues forcefully that mere belief in God’s existence is not enough to save a person. The rebel spirits known as demons are absolutely certain that “there is one God.” They served in God’s glorious presence before rebelling against him. (Jude 6 and study note) So there are no atheists or agnostics among them. Yet, they have no true faith. Their belief in the simple fact of God’s existence gives them no comfort and certainly no hope.​—Compare Lu 8:31 and study note.

shudder: Lit., “they are bristling up.” The Greek word can be used regarding humans as well as animals when their hair stands on end, such as from fear. (Compare Job 4:15 and Jer 2:12 where the same Greek word is used figuratively in the Septuagint.) Here James does not refer to the kind of wholesome, godly fear, or respectful awe, that moves a faithful servant of God to reject what is bad. (Compare study note on Heb 5:7.) Rather, James refers to the sickening dread that the demons have of the all-powerful One who has promised to subject them to the punishment that they rightly deserve.​—Compare Mt 8:28, 29; Lu 4:33, 34; 2Pe 2:4; Jude 6 and study note.