I think you're starting to get it. God planted a sense of judgement in our hearts so we have an innate awareness of what is right & wrong from the start. He created the standard of good so we know what to judge against. Plato thought similarly.
I'm not sure why you are "befuddled." The Bible outlines how we are to discern truth (through God's written word and with the Holy Spirit). You cannot have a relationship with Jesus if you ignore His truth. Thus, the Bible. Romans 12, James 1, etc. Hebrews 4 says it pretty good I think:
Hebrews 4:12 -
"For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart."
The Bible teaches we cannot trust our hearts & minds for they are sinful:
- Jeremiah 17:9 - "
The heart is deceitful above all things, and desperately sick; who can understand it?"
- Proverbs 3 - "
Trust in the Lord with all your heart, and do not lean on your own understanding. In all your ways acknowledge him, and he will make straight your paths."
There are physical differences between sinners of course. But God judges sin fairly and equitably ("for all have sinned and fall short of the glory of God..."). I know it sounds harsh at first. I had the same thought of "how could a loving God do that!?!?" But, when I consider Gods plans are better than my own, I cannot administer justice fairly & equitably but God can, God still has a plan to redeem everyone, and 100 years on Earth is nothing compared to eternity - my perspective changed. But, for those who are or have suffered great pain, I understand why this can be very hard to accept. If thats you Tar, I am sorry for your pain but my hope is to offer hope.