R.C. Sproul: Works do not justify. Faith alone justifies. But faith that does not work does not justify.
It is fascinating to me that R.C. thinks (1) this is faith alone and (2) that this differs from Catholic thought.
Catholics do not believe that we must do anything in order to be part of the Body of Christ - God's mercy is so gratuitous that we may baptize our infants, who can do nothing. Pope Benedict XVI, saying nothing different or new, said that Catholic thought is compatible with "faith alone" as long as faith does not abandon love. (Gal 5, faith working through love.)
One must understand what one truly believes as well as what the other truly believes in order to have real disagreement.