Another argument for God.

[Aoi Magi]

1. The brain is very complex.
2. Humans throughout history have not understood the brain.
3. If the brain is the source of morality and goodness,  then most of humans throughout history have not understood how that is even possible given they have not understood the brain.
4. If we don't know it's possible the source of morality and goodness is the brain and naturalism is true (no spirits, no mystic reality, etc), then we aren't justified in belief in morals and morality.
5. If we aren't justified in beliefs in morals and goodness, then goodness is an illusion.

1. Yes the brain is complex, but so is a rock or a flower....

2. Yes humans are dumb and don't understand a lot of things, like let's say plants are all around us, yet we still have very little understanding of a plants sensory processes. However, just cause we don't know the finest details doesn't mean humans lack a general understanding of the subject. Humans have been poking and prodding at the brain and have known it's importance for a very long time now.

3. The brain is the source of thought. Morality and goodness are social constructs. A cat has a brain, yet it steals food and doesn't find it immoral. Similarly a human baby will pick up any random shiny thing without any concern regarding the ownership of the item. The concept that stealing or taking other's things without permission is wrong, is taught to them by society as they grow up.

4. Why? We are justified in believing in morality because without it our society would fall apart, and this directly effects our own chances of survival.

5. Again, why wouldn't we be justified? and goodness an indeed be an illusion depending on how you define it, but that doesn't invalidate it's existence.

I can't get to your other points as they rely on these premises which I find faulty.