Passage
Thou believest that God is one; thou doest well: the demons also believe, and shudder.
Thou believest that God is one; thou doest well: the demons also believe, and shudder.
James 2:17 Even so faith, if it have not works, is dead in itself.
James 2:18 Yea, a man will say, Thou hast faith, and I have works: show me thy faith apart from [thy] works, and I by my works will show thee [my] faith.
James 2:19 Thou believest that God is one; thou doest well: the demons also believe, and shudder.
James 2:20 But wilt thou know, O vain man, that faith apart from works is barren?
James 2:21 Was not Abraham our father justified by works, in that he offered up Isaac his son upon the altar?
The verse centers on "thou", "believest", "doest", "well", "demons", and "shudder". It is saying that the verse draws attention to "thou" and "believest", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 18's "Yea a man will say Thou hast..." into verse 20's "But wilt thou know O vain man...", so "thou" and "believest" belong inside that flow. In James context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "thou" and "believest" with trust shaped by these words, not by a vague optimism outside the passage.