If we are saved through faith alone, faith in what?

A lot of people in today's world are confused by Eph 2:8-9 because they don't understand that the works Paul was referring to in that verse were the Mosaic principles such as the dietary laws, the observance of festivals, circision and the like which some Jewish Christians thought that they were still obliged to keep. Paul emphatically rejected that idea, because no matter how strictly a person kept the law of Moses, it of itself would not bring salvation, which comes only through Christ because of His atonement. Numerous scriptures emphasize that we are to work out our salvation with trembling and fear. Paul said in another place, utilizing a whole chapter on works, that faith without works was dead, saying, "show me your faith without your works and I will show you my faith by my works." I consider faith an action word which impels me to do those things Christ emulated.