The sinner's faith adds nothing to the Gospel, any more than the windows of our houses add to the light of the sun. The sun shines for everybody. My window lets the light into my room, so that I enjoy it and am warmed by it.
In like manner the sun of divine grace is shining for everyone. Faith is the window which lets the light and warmth of it into the soul of a sinner. If you appreciate that grace, and rejoice in it as the only thing that could possibly meet the need of your soul, you need have no question as to the nature of your faith.