So how does God's forgiveness and our obedience to Him work? What is God like, forgiving or demanding? How should that affect our behavior?
Evidence is subjective to the hopes and fears of the beholder.
Not good evidence. :)
Yes, and I knew you or someone else would say that but I just let it hang in the air.
Trouble is "good" is a subjective word now isn't it?
The truth is that people have to decide what they're going to believe and it's not as based on reason as we'd all like to think it is.
For example, science has shown (heh heh) that the human mind is highly malleable to suggestion and context. Consider, among other things, the classic experiment where the experimenter asked "how much broken glass was there?" vs "was there broken glass?"
That is true to an extent. But once you get past the absolute reductionist/sophist arguments of "does anything outside of my own mind exist" - there are progressively more and more objective evidences and proofs.
Personally, I qualify "good evidence" as evidence that would be immediately convincing to the vast majority of both experts and lay people - either on its own, or when combined with other supporting material (scientific or mathematical theory, corroborating sources, even eyewitnesses in some cases though they are notoriously unrealible, etc.), and where ever possible, is falsifiable and has passed muster via peer review or other confirmation.
There is, unfortunately, quite a lot of our ancient history which does not meet that burden, and some things must be taken on faith. The standards there change quite a bit - but I still maintain that they should at least not include contradictory accounts, and not require abandoning large amounts of knowledge that has been acquired since in order to explain. The more extraordinary the claims, the more extraordinary must be the evidences for them.
The problem with your historical argument is that a lot of things we know about history don't have the sort of historical record that the existence of Jesus has. If you're going to say that Jesus never existed, you might as well throw in the Tannaitic rabbis with them. I've heard people insist that Jesus never existed and that his teachings were mostly adaptations of Hillel's. To them I say, how do you know that Hillel existed? He didn't personally record his teachings. His weren't put to paper (that we know of) until generations after the Gospels were written, and he lived before Christ. Of course, that would still lead one to wonder how the school of Hillel popped up out of nowhere. But, if that's a compelling argument for Hillel, then it would be an even more compelling argument for the existence of Jesus.
Since Paul fairly certainly existed, and since the secular scholarship generally claims that Paul's earliest known epistle, 1 Thessalonians, was written ca. AD 50, you have to at least grapple with how, within less than two decades, a Christian community sprung up that was capable of convincing rather educated people that a man who never existed did, in fact, exist. An, unless you think the contents of Paul's letters are entirely fabricated, despite all the evidence to the contrary, you have to accept that even before Paul, there was a group of people running around Judea telling people that a man of celebrity status had recently been been publicly executed amidst large mobs when the man hadn't even been real. And apparently a not insignificant number of people believed them.
The whole history of the period would require some sort of undocumented mass delusion for your "Jesus never existed" hypothesis to hold up.
Ah well, given that I did not read The Shack as Holy Writ...
I found it to be an interesting parable describing how one particular man found himself visited by His grace and forgiveness, and how that particular individual interpreted the presence of the Trinity.
Looked at from the perspective of a parable, viewed through the prisms and filters of the narrator's experiences, the author's rather radical description of God manifesting Himself in female form is understandable. Consider the multiple, and differing, not always human Manifestations of God thatappear throughout the Old Testament. Consider also that Jesus used parables and language geared towards the understanding and sophistication of his audiences. His sermons to workers are recorded as quite different from his replies to His interrogations by the "scribes and Pharisees" and Pilate.
Getting past the Manifestatin of the Trinity and the Angels,I did find the book had a very Christian message about allowing the light of God's grace to enter a soul filled with the darkness of hatred.