I fully agree to your claim: God cannot be the cause of the “propensity to sin and disobedience”. This propensity entered the world through the first sin in human history, which may have arrived generations after “one human pair was initially given immortal souls” (in Christy’s wording).
Since these primeval humans were created by God through endowing evolved Homo sapiens creatures with immortal souls, they shared the selfish evolutionary mechanisms. Accordingly God endowed these primeval humans with “original grace” to make them capable (as you very well state):
However one could still ask why God created the world through this kind of selfish evolution “at the cost of great pain and suffering”.
Certainly creatures without immortal soul are not capable of sinning and therefore the “pain and suffering” pervasive in evolution cannot be considered a moral evil. Nonetheless it originates from God after all. So what is it good for?
Jim Stump advances very good reasons in this thread.
Additionally, I find illuminating the following quotation by Richard Dawkins:
“We should not live by Darwinian principles […] one of the reasons for learning about Darwinian evolution is as an object lesson in how not to set up our values and social lives.”
This means: One reason because God created the world through “selfish evolution” is that we “learn” by contrast “not to set up our values…by Darwinian principles” but according to moral rules and law.
Accordingly, God is not accountable for Auschwitz but the humans who freely caused such a great pain and suffering.
OK. But a friend of mine recently objected:
In case of a child with cancer the evil cannot be explained by saying it is caused because humans freely decide to do something wrong.
That is true. Cancer is a consequence of the mechanism of evolution. Consequently my friend’s objection amounts to say that:
If God exists He should not allow innocent people to suffer.
We are faced here with the theodicy question or “the problem of pain” after all:
Either God doesn’t exist or suffering has a meaning we don’t fully understand.
The conversation with my friend continued as follows:
AS:
Then try you yourself to heal this pain as you want God should do.
My friend:
I am not capable of that.
AS:
So you acknowledge that you cannot be like God. By permitting pain God is helping us to acknowledge we are not almighty, that is, He help us to avoid falling into temptation to want to be like Him without loving him. Such a help is actually a good thing for us on the part of God.
If we acknowledge that God is almighty and we not, we will be moved to ask God for help. Undoubtedly we should make our best to increase scientific knowledge and find means to overcome pain. But at the same time we should realize that we are and remain always limited beings, and thus never underestimate the “power of prayer”.
In summary, God used “natural evil” as an ingredient to create the world to move us to atone and long for Him in case we sinned. However He endowed the primeval humans with “enough (original) grace” so that He could not be blamed for having induced them to sin.