The difference is our response to information. The actions of the response are the outer works resulting from our inner decision. Faith is the seed which grows into works based on an affirmative hope. Doubt, on the other hand, chokes the hope out of faith and leads to denial. When it comes to the Good News of Jesus, faith leads to hope in eternal life whereas doubt leads to denial of the Lord and His grace.
This post is an excerpt (Question 6.9) from my book Ask James one.