When you really, really get it, you do the good works. If you aren't doing the good works, you don't really have faith, even if you say/think you do.
Which is all kind of abstract.
The concrete version:
I'm sure you know some good people. You can count on them to do good things, as a consequence of their character. Good is a state of being for them, rather than an action. You might also know some complete jerk who does something good from time to time, but it isn't part of his character.
In spanish, there are two different words (each with the whole conjugation mess) for "is" in order to address the situation. "Esta" means "is right now" and "Ser" means something like "is, by it's nature."