Writen as a reply to Estlor's "On the Nature of Magic" which, in my (Warlocke's) opinion is very good with yet a few flaws...:

I'll start out being picky, just to get that out of the way.
>The elements are typically not found alone in substances.

True that elements are not typically found alone in substances. In fact, the only substances all elements would not be found in is the elements themselves. No fire in water no air in earth, etc.

>For example, the correct balance of Air, Earth, and Water forms
>the typical thunderstorm.

Actually, its the correct balance of all elements to form the typical thunderstorm. Without fire, theres no lightning, without shadow, its light out, without force, theres nothing (at least no motion)

>One who studies and casts Air spells as their specialty can be
>called an Air Elementalist or an Aeromancer. With their control
>of Air, they have power over the winds, breath, and all
>types of clouds.

All types of clouds? not actually so. cloud is a mix of 1 part air , 1 part water, very small amounts of the other elements. the ideal Aeromancer has 50% control over your average cloud

>Earth is the most present of the elements. Practically everything
>we see is fully or partially related to Earth

(everything that is except the other elements) but what exactly is earth? is it the soft dirt beneath us, or the hard stones that break our bones? [authors note: please excuse the poetic insert]

>Fire is the factor of change. It destroys without utter
>destruction. Whatever it acts upon is transformed into another
>form.

Fire has an obvious weakness to water, if fire is the factor of change then does is not also have an innate weakness also to earth on which it feeds and air with witch it FUELS

>With Fire, they gain control of all forms of Fire, Light, and
>Heat (this typically includes standard fire, microwaves, lava,
>and plasma).

not microwaves. microwaves are not heat or fire-like, they are waves just like radio waves. they way it works, why it is associated with heat that is, is by being on the exact same frequency as water, thus transfering all its energy into water, creating heat from energy because when you add energy to an atom, it moves faster which increases kinetic energy which produces heat and sometimes light. but i wont go into all that...
As for plasma, all elementalists have control over plasma by simply raising the kinetic energy of any of thier elements until it attains "plasmatic" state : )

>The element Water is the second most present element...

I'd personally stay away from saying any one element is more present than another element

>Someone who specializes in Water can be called a Water
>Elementalist or an Aquamancer. They control the three aspects of
> Water: Water, Ice, and Cold.

Not so (sorry to say) but no elementalist has control over cold (though an aquamancer may have an advantage as far as causing it)

>Lightning can also burn off clouds.

I have no idea how this would be possible.

>Air and Earth are slightly less biased against each other...

I'd have to say they have about the same amount of bias between eachother as fire and water, its just at a different level. volume as opposed to temperature perhaps

>The Fifth Element: Shadow

Shadow, or darkness or whatever, is the opposite of light. Logically, light is then an element also if Shadow is one

>The fifth element is the opposite of the first four.

I would like to point out that earlier earth was the opposite of air and fire was the opposite of water, now shadow is opposite of all four. This creates 3-way opposites, which may not be possible, its something someone might want to write a rely on...

>When you['re] arm cast its shadow, why did it not destroy the
>objects it was cast on?

About this analogy: Inside the element Earth, there is nothing but shadow... wouldn't this cause anything with earth to instantly attain total internal combustion? You'd probably reply something like "but the force is all throughout earthe*, thus keeping shadow at bay". But what about the other elements... fire then doesn't need force because it creates light, and air and water only need force when no fire is present. This means that force would have to favor earthe... such an ominously binding element as Force shouldnt favor any one element...so i suggest there is a flaw in the logic.
* I decided that earthe = the element earth, to help rid of confusion

I won't go into the Folklore & Myth section, because it's folklore and myth : )

About the Spheres: I thank you for the invitation, Estlor, and I accept. I will get to it when I have time (and seeing how long it took me just to get to doing this, don't expect my thesis anytime soon: )

Final note to Estlor: Perhaps you should rethink Shadow as the fifth element, and have Light and Dark as the fifth and sixth elements (not necessarily that order). Then have Force as a seventh element, which not only protects the first four elements from darkness consuming them but also stops light from destroying them (perhaps by overheating, or hazardous bombarding of photons or something...you know)