The Word of God.
His words says,
for fall have sinned and fall short of the glory of God
and that then means we are not good, right? He also says,
None is righteous, no, not one;
no one understands;
no one seeks for God.
All have turned aside; together they have become worthless;
no one does good,
not even one.”
When we compare ourselves to God's standard, His law ~ The Ten Commandments, then we will find that we do fall short. We have broken His commandments and are therefore we are GUILTY.
But you may say, I have not broken ALL of the law. I haven't murdered. I haven't stolen. Well, according to God's word you don't have to break all the laws to be guilty.
For whoever keeps the whole law and yet stumbles at just one point is guilty of breaking all of it.
The makers of the "180" movie have just produced another film about false conversion. I encourage you to take a few minutes (just 34 minutes) and view it.