Is our faith working or worthless?
The profession of our faith (our words) is no good unless we have works to back up our statement of faith.
How do we know a person's belief is true? It produces fruitful works.
Faith without works is dead. We are justified by faith unto salvation without any works (cf. Eph.2:8-9; Rom. 4:3-5). But our salvation is justified (i.e. we are proven to have a real saving faith) by the works we produce (Jas 2:21-22).