Why are the Ars Arcana inaccurate?

[Neithan]

If Khriss wrote the Ars Arcana, why do those of the Mistborn books contain inaccurate information reflecting what the characters in the story know? If Khriss is really compiling the information about the magic systems, why would she be limited to the current knowledge of the characters?

For example, The Well of Ascension has a metals table with atium and malatium as the external temporal metals, which we know is incorrect. Also, each successive Mistborn book contains more metals in the Ars Arcanum than the previous. It seems unlikely that Khriss wouldn't know these things until the characters discover them in the story.

[The One Who Connects]

2 minutes ago, Neithan said:

If Khriss is really compiling the information about the magic systems, why would she be limited to the current knowledge of the characters?

Because Time-Travel doesn't exist. How is she supposed to learn about something if there's nobody to learn from?

Alendi was one of the first Allomancers. The only people who knew anything about the other Metals were the Synod(who were in hiding, and by HoA, all dead) and the Lord Ruler, who doesn't allow interviews.

Khriss was only allowed the scraps of knowledge that TLR allowed anyone to know. The Steel Inquisitorius is responsible for Atium being in the Temporal Quadrant, and as the only ones who've experimented with it, they are the most authoritative source. This is also why the Atium steals anything tidbit didn't exist yet, because the Inquisitors hadn't discovered this until Ruin was freed.

MB Era 2 Spoilers(on the assumption that you haven't read it yet)

Spoiler

From a technological standpoint, Bendalloy couldn't even exist until Era 2. One of the only reasons people learned it was an Allomantic Metal was because Harmony gave Spook a hint that led to Cadmium, and they searched for an Alloy. If this hadn't happened, there's no way Khriss would know about the metal to include it in AoL's Ars Arcanum.

It's the same on Roshar, where there haven't been Surgebinders in nearly 2,500 years, and 4 losses of information since then(The Recreance, The Hierocracy, The Fire in the Palanaeum, etc..). She can't learn what nobody knows.

[Shqueeves]

It's because the Ars Arcana are written at about the same time as the story. As more metals were discovered, she updated her notes. 

[RShara]

Khriss is working off of what she can find out from the people in-world and the AAs are written at or around the time period of the books.  Sadly, she is not all-knowing, so she can get bad knowledge.   She's written as a researcher and scholar, rather as the Author (as in Brandon).  She has access to more sources, perhaps, but still is limited to what she can find out.

[Neithan]

1 hour ago, Shqueeves said:

It's because the Ars Arcana are written at about the same time as the story. As more metals were discovered, she updated her notes. 

Ah, I had forgotten that Khriss was on Scadrial at the time of the story.

[theuntaintedchild]

12 hours ago, Shqueeves said:

It's because the Ars Arcana are written at about the same time as the story. As more metals were discovered, she updated her notes. 

This makes me wonder when approximately her entries in Arcanum Unbounded are supposed to have been written. It's known it's before SotD. But where in relation to Mistborn and Stormlight does it take place.

[Weltall]

2 hours ago, theuntaintedchild said:

This makes me wonder when approximately her entries in Arcanum Unbounded are supposed to have been written. It's known it's before SotD. But where in relation to Mistborn and Stormlight does it take place.

Brandon has said that they were all written at the same time and are contemporary with 'most of the books'. Context clues tell us that it must be some time between Hero of Ages and Sixth of the Dusk and Brandon's comment suggests it's somewhere close to the events of Stormlight Archive/Mistborn Era 2.

[Andy92]

I was personally pretty confused about how some of the metals were supposed to be categorized when I first read the series. I didn't realize at the time that the Ars Arcanum were supposed to be written from the point of view of a character. While it's a cool idea, I found it a bit confusing when I first started reading the books. 

[theuntaintedchild]

20 hours ago, Weltall said:

Brandon has said that they were all written at the same time and are contemporary with 'most of the books'. Context clues tell us that it must be some time between Hero of Ages and Sixth of the Dusk and Brandon's comment suggests it's somewhere close to the events of Stormlight Archive/Mistborn Era 2.

Thank you. That's what I suspected. As for some reason that era seems to be the most present of the books. Maybe because I'm having to wait in between books.