I want to write stories for Christians--good, clean stories that are the kind I like to read. As such, these principles are the cornerstone of my writing.
God is the Incorruptible. One way to define Incorruptible is always new. Another is infinite diversity.
God made people in his image, and he intended them to be infinitely diverse too. He meant every person to be a unique universe, to express some unique facet of the Incorruptible. One may see a shadow of this in a bookstore, in all the worlds that people have created.
When, however, people try to make themselves diverse or original by means of corruptible power, they must fail. Corruptible power is subject to entropy, and the end result of entropy is a universe where everything is the same. And when everything is the same, then everything is dead.
So, we should write what we've got. Write what we like to read. Write the treasure God put in us to get out, and don't worry about making ourselves original. God will take care of that.
"What thou seest, write in a book..." (Revelation 1:11)
Corruption versus Incorruption
I have encountered at least one Christian fiction author who claimed that explicit depiction of evils such as adultery or profanity were useful to show evil for what it is. Ironically, however, the only way to truly understand the horror of corruption is to see the Incorruptible. That is what happened when Job came face to face with God:
"I have heard of thee by the hearing of the ear: but now mine eye seeth thee. Wherefore I abhor myself, and repent in dust and ashes." (Job 42:5-6)
Job thought he was a pretty good guy, until he saw God. Similarly, morality may seem to us like shades of grey, where good and evil are mixed together, until we too see the Incorruptible.
For there is no corruption in incorruption, nor is there incorruption in corruption, and the war between them is the story of our world.
Little by Little
According to Jesus, his parables hid the truth, whereas his interpretations of those parables plainly revealed the truth. The same might be said of Christian fiction versus non-fiction. Christian fiction is about hiding the truth.
So, a Christian story may be written to Christian principles without ever stating them. That is, the story doesn't have to be a morality play or include overt evangelical passages.
Similarly, even from a mechanical perspective, fiction should hide as much as possible from the reader. Or to put it another way, the story should develop plot and characters and descriptions little by little.
Christian non-fiction, however, is all about plainly revealing the truth. Nevertheless, even there the truth should be revealed little by little. The Incorruptible is infinite; it's impossible to exhaustively describe the truth. There's always more to see.
"For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little..." (Isaiah 28:10)