A note on doubt: You may find it helpful to point people to a 3 page article on doubt by John Dickson that we have posted at evchurch.info/doubt
Importantly, notice that James calls the person “double-minded” (verse 8). That suggests that their main problem is a rebellious heart: they have a foot in God’s camp but also a foot in the world’s. That’s the reason for their doubts, rather than the more innocent intellectual questions or feeling of uncertainty that creeps up for many of us from time to time.