yes, it DOES. Harry specifies information, tells exactly what it does, and then gives an example of what it's been used for. There is no indication that Harry isn't Doylistly supplying information for the audience... Something done literally all the time. And you couldn't use the placard in such a way, if sin WASN'T a quantifiable force. Pls don't confuse irl prejudice against christianity to mean you have to argue against fictional christianity...
Alright, let's get a few things straight
Sibelis.
You don't know me, so don't presume to know my views or beliefs. This forum is one for the discussion of spoilers pertaining to the Dresden Files series. Attack my arguments by all means but steer clear of attacking me. It's entirely inappropriate to comment on or speculate on my religious beliefs (or lack of as the case may be). My beliefs are and views are irrelevant and no one else's business, nor are anyone else's on this forum. So I remind you that such speculation and discussion are against the rules of this forum and I invite you to engage me based on the points I raise in my arguments, not speculate on things that are outside the purview of the topic. I understand you might feel that I attacked something you believe in, but I did not, and to do so would have been wrong of me.
I am not, and was not, attacking or otherwise railing against Christian beliefs. My argument was clear enough and if you read it back carefully you will see that I disagreed that the passage "shows" what you claimed. I did not say that Christ didn't die for the sins of humanity or sin wasn't real, I stayed well outside our real world and made no definitive statement or position on real world topics and would ask you do the same. Do not mistake my tone for anger. I am being direct because it is necessary in order to have respectful debate on this forum.
Now to your argument itself.
1. How does the scene "show" sin in a quantifiable way, how does it show Christ died for the sins of humanity in the Dresden Files? "Show" means to cause something to be visible or perceived. In what way was Sin or Christ's redemption visible in that scene?
An example of something (such as a force) being shown in the series is Soulfire. In SmF Harry first shows an application of Soulfire (even though we do not yet know what it is). We later get a small explanation from Mab to what it is, and further from Bob. An excellent scene with both exposition of the force that is Soulfire and the application of it is during Cold Days when Harry contests with the will of Mother Winter and breaks the bonds laid on him.
In no way does the scene in which the Placard is used show sin.
Mac was a lean man around six feet tall with broad‑knuckled hands and a shining bald pate, dressed in his usual black slacks, button‑down shirt, and spotless white apron. He’d been a friend for a long time. He looked at me and then nodded toward his pantry and office.
Karrin and I walked over and went in. Without a word, I opened up the backpack, took out the little wooden sign, and put it down carefully on his desk.
Mac saw the sign and his eyes widened. He looked at me, his face written heavily with consternation.
“You know what it is,” I said.
Mac rocked back half a pace. He looked from the sign to me. He didn’t quite lick his lips in nervous guilt, but it was pretty clear that he didn’t like that I’d realized what he knew.
“A lot of the Paranetters are here tonight,” I said, “because we put out an alert yesterday and this is one of the designated shelters.”
Mac nodded firmly.
I met his eyes for as long as I dared and said, “What’s coming could kill every one of them. So I need your help.”
Mac looked from me to the sign and back, grimacing.
“Mac,” I said quietly. “Not just anyone would recognize that sign. I mean, it’s just an old piece of wooden board, right?”
His expression became pained and he held up his hands.
“There’s a Titan coming to Chicago,” I said, “with an army, courtesy of the Fomor, to burn the place to the ground. They’ll be here in maybe an hour. There’s no time to get cute. Are you willing?”
He frowned. He stared at the sign for a second and then away.
“Mac,” I said, “there’s no time for this.” I bowed my head, rested the fingertips of one hand against my temples, and began to call up my Sight.
A wizard’s Sight is a powerful tool for perceiving the energies of the universe. It gets called a lot of things, from dream sight to the third eye, but it amounts to the same thing—adjusting your thoughts to be able to perceive magical energies as they move around and through the natural world. The Sight shows you things in their purest nature, reveals fundamental truths about people, creatures, and things that you look at.
A while ago, some of the Outsiders had come looking for trouble at Mac’s.
They’d recognized him.
I didn’t know what Mac was, but it seemed clear that he wasn’t just your average bartender. I figured it was about time we got to know each other a little better.
But before I could look up, Mac pressed my hand gently against my face, making it impossible to open my eyes.
“Don’t,” the mostly mute man said gently. “Hurt yourself.”
He didn’t let me move my hand until I’d released my Sight—and there was no way he should have been able to know that. But he did anyway. Which put him in a relatively small pool of beings—those with a connection to divine knowledge, to intellectus, and given what the Outsiders had called him, I was pretty sure I knew what Mac was now. Or at least what he had once been.
He lowered his hand slowly, his expression resolved. Then he took a step back, pursed his lips, looked at me, and shook his head. After that, he moved briskly, opening a storage cabinet and taking out a small, efficient toolbox. A moment of effort and he’d put a couple of screws in the back of the sign, connected by a strand of wire.
“What is it?” Murphy asked as he worked.
“The placard from the Cross,” I said. “The one that said, ‘Here is the King of the Jews.’”
Her golden eyebrows went up. “From the vault?”
“Yeah,” I said.
“What does it do?”
“It’s embodied intercession. It focuses energy on an individual,” I said. “Something about pouring out the accumulated sins of humanity onto Christ, maybe. Hang it up and it puts up a kind of threshold that will hold off just about anything supernatural, as long as the property’s rightful owner is alive.”
Mac took a small folding knife out of his pocket, opened it, and pricked his thumb. A drop of blood welled.
“So everyone here will be safe,” Karrin said.
Mac hesitated for only an instant. Then he took a deep breath and pressed his thumb against the back of the placard, smearing his blood there.
“Anything that wants to get to them will have to go through Mac first,” I clarified quietly.
Mac took out a nail and a hammer; then he tucked the placard under one arm and walked out with them. A moment later, we could hear him using the hammer as he hung up the sign.
Where in that body of text is the force that is Sin shown? Where is the exposition or depiction of Christ redeeming humanity? It isn't there.
“Something about pouring out the accumulated sins of humanity onto Christ, maybe.
This is the only bit that even references it, and Harry thinks it is a
maybe. It is unclear, uncertain, and lacking in detail. Which is part of why it's in there. For us readers to speculate on and for Jim to perhaps lay some ground work. It certainly doesn't connect how even the event of pouring the "accumulated sins of humanity onto Christ" would create an "embodied intercission" or what it had to do with Christ's redemption of humanity. It's not facts, even in-universe, it is speculation. Whether the event (read:crucifixion) happened in the Dresdenverse (seems likely) and what was actually going on beyond the torture and execution of God's only Son has not been stated. Some on these forums believe Jim will never make a definite statement about it at all. I suspect he will but currently we have next to know facts about the event. Using real world information from our universe is good for speculation but ultimately is still not fact and you can be sure Jim will have his own take. But we must be careful not to confuse a work of fiction with an event in our world.
Even if you believe Harry is Doylistly (as you put it) supplying the reader with information, it isn't clear in-universe how he came in possession of such high-level information (unless you believe any old person in the series could just find out). So the fact remains that either it is poor writing and Jim just forgot to mention how Harry actually found this out OR he is setting it up for later. Which is more likely.
I have no idea what you mean when you say that you couldn't use the Placard in such a way if sin WASN'T a quantifiable force. The scene explains how the artifact can be used, sure. But it doesn't say how the artifact came to be this way. It was just a sign originally, as far as we know. It's association with the Crucifixion and Christ is likely (but not definitely) how it gained it unique properties but we don't know for sure, as Jim hasn't yet explained that. Even Harry doesn't know - he is merely speculating.
The closest we have come to seeing something like Sin is the corruption that Lasciel and Anduriel have displayed. Lasciel mentions that the Fallen are corruption, and Anduriel shows his influence in Skin Game when pulsing while Nicodemus is having a monologue. But even there it isn't explicit. So for now, it's as much a metaphor in the series as love (in fact more so).