But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him. (Hebrews 11:6)
A saving faith is one that will trust wholly and completely in the merits of Christ's shed blood to save them (Hebrews 9:12). It is 100% by Christ alone and 100% by His grace alone that you can be saved (Romans 3:23-24).
Anyone who possesses this kind of faith recognizes their own sinful condition, understands that Christ alone saves, and they also have the assurance that Christ's atonement applies to them personally.
But a saving faith is also an active faith. For the true believer, there is always a change in the pattern of sin. Faith that does not bear fruit is a dead faith and cannot save (James 2:17).
The fact is that faith "alone" will not save unless it is the kind of faith that Paul talked about in Galatians 5:6 -- faith expressing itself through love. Anything short of this dilutes the meaning of faith.