The Basics of Quintessence: A Philosophical approach to Magic Written by Merlin the First Chapter 1: Magic: Wherefrom and Whence

The Laws

To understand magic, one must understand the laws that govern its usage. Basic laws of magic shall be the next 2 chapters.

Near-Equivalent Exchange

Humankind cannot gain anything without first giving something in return. To obtain, something of value must be lost. This is Magic's first law. Magic like all forms of energy requires payment for the actions it will perform. A body must require food to continue to provide the energy to stay living. Plants the energy of the sun. The waterwheel needs the force of the river to grind grain. For a practitioner of magic to produce an effect, energy is used from the practitioner for payment. Not always is the value of said activity immediately knowable by an apprentice practitioner of magic, but one gets a feel for it with time. To know ones ability to give in order to receive comes with time and practice. In my days we have been able to narrow costs down to a science, and with arithmetic able to successfully plot out energy costs for many of our actions. The energy that we use in our works is up to debate on where it arrives and where it resides. A novice mage will pull from the reserves of his vitality, but as he matures he gains a reserve that does not fatigue nor does is pain. We call this Magical Threshold. As one matures as a mage the threshold increases, and the effects that a practitioner can perform grows as well.
The source of this Threshold is in contentious debate for many practitioners. The godly will pronounce it as the grace of god to change the world entrusted into their hands. When said faith is lost their abilities drain as well, supporting their hypothesis. However, not all practitioners are servants to gods and supernal forces, many respect Gaia, and believe her to be the source of all power. Low and behold, when reverence to Gaia has waned in the hearts of such men, their ability weakens. So on and so on for practitioners of many arts such as Arithmancy, Spodermancy, and Necromancy.
The main theme of said magics is belief in power. To accept in the power of an idea provides power. This is half of the reason for the "near" in Equivalent Exchange, as belief strengthens belief, nothing is truly lost outside of time and wits.
So if in purest form magic is power and power is energy, a belief that this is true creates magic in its purest form, which we call Magery. To accept magical fundamentals at it's purest and most calculable form is Magery. To limit it to beliefs outside of pure magery is called College Magery. A Mage with belief in the power of the flame will call himself a Pyro(Flame)-Mancer(Practioner of a Magical College). His College name would be the Fire College (or flame, names will settle themselves out in time.) Limiting oneself to a college allows faster growth as a mage compared to one of Pure Magery, put at the cost of focus in his College, and the limitation of using his magic only in his medium.

The Other Half of Near

Like a ship at sea must take into account of the variables of the ocean, magic loses equivalency to chaos (hence known as Entropy) of the world. As an ax chops a tree, energy comes back to the ax dulling the blade. Power is lost in open systems, so an arrow will fall and a bolt of energy dissipates with time. A mage must know to put extra energy out when creating effects. Curses wain with every day as the magic finds its way back to wherever it was before.

_{Modern mages are amazed the magical knowledge of Merlin, but not his grammar.}