Arcanists and their spells

[Kerberon]

Here's a picture of some chemicals from our world. Looks pretty similar

[Nahara]

The books are indeed magical, as are the ink. Two texts from the Relic Reborn quest for the Omnilex and the Veil of Wiyu stand out:

Turns out the patterns on the cover are meant to improve the flow of aether from the wielder's hands. An' I'd thought 'em merely decorations. Ye learn summat new every day, eh?

I thought that the studs what adorn it were only good for holdin' the bloody thing together. But it turns out they're meant to channel the wielder's aether as well. Ye learn summat new every day, eh?

So we know that, at least in the case of the Omnilex and the Veil that the bindings of the books are designed in a way to better channel aether. Now, onto some text about the ink:

Ink fortified with X sand to improve aetherial conductivity.

The X is merely a placeholder for the various types of sand usable in the ink's creation, be it copper, silver, gold, rose gold, or whatever the Superior Enchanted Ink is made of that makes it better than the rest. You can think of it like the conductive circuits on a motherboard (all those copper lines); these lines can be drawn with a pen, so it's stands to reason the enchanted ink used to make arcanima grimories is similar in function, but works with aether instead of electricity.

[EDIT]
So if you really wanted to think it all through: The arcanist opens his grimorie to the page containing all the information necessary about the spell he wishes to cast, which takes the form of arcane geometries. The arcanist feeds aether into the geometries, which shape the aether into the desired form, which is then released onto your target as the finished spell. More advanced and/or personalized grimories can contain additional aetherial conductors as "decoration" on the binding to improve performance.

And thinking on it a bit more as I write this, the grimories are essentially computers for magic. Aether is to electricity, as the conductive ink is to the motherboard, as the additional conductors on the binding are to more RAM or an additional CPU.

[Wadoka]

If you consider again from the aspect of science and mathematics, if you start with good old Ruin and up through Bio, Miasma, and so forth... you could say they are all examples of accelerating the Universal characteristic of Entropy.

A true archetype of an Arcanist would be able to accelerate the corruption, corrosion, decay of practically anything subject to Entropy. This could include massive structures, like the walls of Ul'dah.

A powerful Arcanist would be a siege weapon without parallel.

Now, a good, heroic Arcanist would have also studied how best to *arrest* Entropy... and legendary heroic Arcanists would have myths told of them, of being able to reverse it - healing awful wounds, restoring life to the dead, creating unbreakable, invincible items...

[Kerberon]

A true archetype of an Arcanist would be able to accelerate the corruption, corrosion, decay of practically anything subject to Entropy. This could include massive structures, like the walls of Ul'dah.

A powerful Arcanist would be a siege weapon without parallel.

Most magic wielders would be like gods to any but a magic user if it was taken into a realistic situation. Look at your city walls example. A Thaumaturge could freeze the walls then flash thaw them creating thermal stress that would make them so brittle that a 90lbs weakling could tap on them and shatter them.

[Catapult]

So, it turns out we've talked about this once before. Back then, I came up with this interpretation, which I guess is worth revisiting.

Conjury is the magic of nature. It weaves the aether of nature to manipulate nature, thus making it dependant upon an understanding of nature and its elemental guardians. Earth is uplifted, air is moved and water is gathered. Curing magic re-forms the body to close wounds (enhanced in WHM). It is the magic of motion.

Thaumaturgy is the magic of raw energy. It draws forth the aether of one's own wellspring and by regulating their aether in the astral and umbral polarities, are able to channel the latent aether of the world (and void - BLM) through themselves and into an expression of energy. This takes the form of electrical currents, burning heat, or the icy absence there of.

Arcanima is the magic of matter-alteration. Through the use of symbols, they apply aether to transform the environment around them. This can inflict disease and slowly tear at a victim's biology. It can also cause the aether around them to transform into an entity that bears the consciousness of aether (much like how a primal is summoned but on a smaller scale) and bind it to their will. This bears a greater similarity to ancient Allagan techniques, which may have persisted in Nym and the Southern Island areas in isolation from the Black/White advancements of mainland Eorzea.

Motion, Energy and Matter. Three ways of manipulating aether, all with very different results.

I kind of haven't changed my perspective much and I think it fits with a number of other theories. I particularly like Darske's contribution regarding fractals.

[Niwashi]

I think conceptually, Arcanists should be thought of as both having and using far less Aether than either Conjurers or Thaumaturges. The precise equations used to manipulate it allow them to create major effects even from the sort of small energy expenditures that the body can safely handle. (This is how they avoid the dangers Sylphie and her mother ran into trying to use Conjury from personal aether alone, since Conjury requires a greater amount of raw power.)

This isn't fully expressed in the amount of MP we have and use, though. Which could either mean I'm wrong in how I'm thinking of it, or could simply be a case where gameplay trumps lore (since ACN having/using far less MP than the other casters would make it difficult to correctly balance cross-class skills). Perhaps we could say that MP is simply measured by a different scale for different classes.

But we know that we are writing in the books so what happens to it? What if our book fills up with all the formulas we're writing out?

Perhaps they would fill up eventually. We know that Arcanists normally keep replacing their books periodically (as we do ourselves every time we upgrade them). The only question in this regard is about the Miqo'te girl we train with and the book she's so emotionally attached to. We know it's highly irregular for her to keep the same grimoire for so long, but we don't know why she hasn't run out of room in it.

[Darske]

Maybe she just has really, really tiny handwriting.

[faris]

Possibly it's already been mentioned in this thread but in ONE fieldcraft or tradecraft quest (possibly miner. Unsure. Or even alchemist.) it is mentioned that the ink used to create grimoires is aetherically conductive.

[Niwashi]

Possibly it's already been mentioned in this thread but in ONE fieldcraft or tradecraft quest (possibly miner. Unsure. Or even alchemist.) it is mentioned that the ink used to create grimoires is aetherically conductive.

It's the level 20 Alchemist quest. The explanation given there is:

For an arcanist to weave his spells, he must conjure in his mind the image of distinct mystical diagrams known as arcane geometries. These geometries are inscribed upon the pages of a grimoire, such as the one you constructed at my request. The most important aspect of any grimoire is the quality of the ink used to illustrate its pages. Geometries drawn with ink that is especially conducive to the flow of aether allow the arcanist to more effectively channel his magic strength. Thus when one is in need of a new grimoire, one must turn to an expert in the making of this liquid gold--an alchemist. And, Thaliak be praised, I was blessed with the attentions of a true artist.

The descriptions of the inks themselves refer to it as well. They're "Enchanted <metal> Ink" with various types of metals for various levels (Enchanted Copper Ink, Enchanted Iron Ink, Enchanted Silver Ink, etc.) and the description of each is "Ink fortified with <metal> sand to improve aetherial conductivity." (with, obviously, the name of the appropriate type of metal there).

[Gamma621]

As guildmaster Thubyrgeim put it they are 'esoteric calculations to express the nature of aether in mathematical terms that are represented by arcane geometries.' These are the patterns that allow arcanists to manipulate aetheric energy and produce specific effects. It's also what allows them to shape the aether into summonable entities like carbuncle, the egis, and the fairies.

What I don't understand is how all these complex formulas and spells equate out to things of the biological variety like Bio and Miasma. We get a very clear cut definition of how conjurers and thaumaturges are able to cast the elemental spells that they can. (Nature and harnessing their own inner aether respectively)so why or how do arcanists produce these debilitating poisons and how exactly do they get into our enemies that don't have blood or other things of the biological variety like golems and skeletons and such?

You answered your own question while you were asking it.

If Arcanists/Summoners are able to shape aether into physical manifestations such as the carbuncles or egis, then why wouldn't they be able to shape microscopic manifestations that attack an opponent at the cellular level. They even have a move called "Virus," which means they shape the aether into bacteria to weaken the opponent. Same principal used for Scholars as they manifest leeches to extract disease from a teammate.

I ask because these are things that you would see in the arsenal of an assassin or ninja, not typically a math textbook.

I think you are confusing bio with poison. Yoshida said that the new ninja class will be utilizing poisons, such as weapons coated with Poisonous Potions. Bio implies biological, such as egis, or even bacteria.

After reading through this thread, I think their skills match the class rather well.