This is a bit of a theoretical question, but what is the biblical basis for the belief that non-believers can do good (doing good meaning performing a good deed from a good intent)?
On the contrary, scripture seems to show that humanity is incapable of doing anything good:
Genesis 6:5 ESV, Matthew 23:37 ESV The LORD saw that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually. ... For as were the days of Noah, so will be the coming of the Son of Man.
Romans 3:11-12 ESV 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.
Isaiah 64:6 ESV We have all become like one who is unclean, and all our righteous deeds are like a polluted garment. We all fade like a leaf, and our iniquities, like the wind, take us away.
This seems to go against common sense as we all know non-believers that do lots of good.
I'm not questioning whether or not non-believers do good deeds. I'm wondering, given God's frequent intent through scripture to show how fallen we all are without Christ, where scripture states that non-believers still have the capacity to do good without Christ.