Thou believest that there is one God; thou doest well: the devils also believe, and tremble. Thou believest that there is one God - This is the faith in which these persons put their hope of pleasing God, and of obtaining eternal life. Believing in the being and unity of God distinguished them from all the nations of the world; and having been circumcised, and thus brought into the covenant, they thought themselves secure of salvation. The insufficiency of this St. James immediately shows.
The devils also believe, and tremble - It is well to believe there is one only true God; this truth universal nature proclaims. Even the devils believe it; but far from justifying or saving them, it leaves them in their damned state, and every act of it only increases their torment; φρισσουσι, they shudder with horror, they believe and tremble, are increasingly tormented; but they can neither love nor obey.