James 2:19

Thou believest that God is one

(συ πιστευεις οτ εις θεος εστιν). James goes on with his reply and takes up mere creed apart from works, belief that God exists (there is one God), a fundamental doctrine, but that is not belief or trust in God. It may be mere creed.Thou doest well

(καλως ποιεις). That is good as far as it goes, which is not far.The demons also believe

(κα τα δαιμονια πιστευουσιν). They go that far (the same verb πιστευω). They never doubt the fact of God's existence.And shudder

(κα φρισσουσιν). Present active indicative of φρισσω, old onomatopoetic verb to bristle up, to shudder, only here in N.T. Like Latin horreo (horror, standing of the hair on end with terror). The demons do more than believe a fact. They shudder at it.