One of the original Elventi was the High Elventi known as BlenderofSixElements. Actually at the time, he was StarsFallingAcrossTheMoonastheSnowFalls. All the Elventi knew a bit of magic, the manipulating of cosmic flows to effect the world. He who would become BlenderofSixElements spent the the time to experiment and contemplate the elemental forces of Arth. He creates the rules and functions of magic as it is known in the Known World and taught it to the other Elventi.
The teaching of magic is normally linear, one teacher to one student. That teacher’s preferences colors not only which students they would teach, but which mystical skills they would emphasize. Thus "bloodlines" of mages were created. One could tell who one’s mentor (and who his mentor and mentor’s mentor was) by their attitudes and skills. Given the immortality of the High Elventi, many bloodlines came from the prime source. It is from the "pure bloodline", a "recent" student of BlenderofSixElements, ImpatientShaperofTreesWhoCastsRatherThanShapes (an Elventi who changed professions radically) that Humanti magic came from.
The Magic Guild is one of the first Humanti Guilds, one of the first organizations that crossed clan bloodlines. They began to adapt what they had been taught to the "human time". "Caster" as they came to call him, eventually came back and taught the Humanti more completely, allowing the council to become the first Wizards.
Since magic was innate to so many parts of Elventi culture, magic was one of the avenues of uplifting/ civilizing Humanti. They learned the basic truths of language, mathematics, the nature of the universe, religion, and the flow of cosmic forces.
All six elements in their manifest and higher form were initially taught. The Humans would tamper with things on a small scale using thigns of the fifth (light and dark). This created imbalances that needed to be addressed. After a particularly bad wave of weather caused by Human miscasting, the Elves, realizing their mistake, threatened to kill off all Humans - even though they were Imperial Citizens. A compromise in court was immediately implimented. They left Lumenos (light and dark) to the prayersmiths (those who follow The True Gods of Arth), who might invoke a spirit to work any effect. The other elements were allowed to be touched by all SpellSmiths.
To give you more system
Magic is skill based. Each element’s aspect (there is one to three per element), is its own skill. If you have a small number of skill system, break it down to the elements, if you play GURPS each spell is a skill, if you play Hero, each is its own power set. Apply as it is best fit.
For those who have not read an Arth Post, like the Gods
Fire (Fire, Motion)
Earth (Earth, Mind Control)
Air (Air, Perception)
Water (Water, Healing)
Light (Not allowed)
Darkness (Meta Magics only)
Each spell is empowered by Mana, a personal magical endurance/ power of your spirit/ metaphysical constitution. Thus spellcrafters can cast a variety of spells a day. They can only cast a short number of spells at a time, though they might recover power during the day. Figure 12-16 points of mana, recovering one point per hour, each spell taking 1-3 mana to cast.
Each spell has matching Cards in the Arthian Tarot Deck. In fact, the Cards are used as training tool in this system of magic. So never play poker with a spellcrafter.
Now the Philosphy behind this spell system is the same as the underlying system of philosophy for everything in The Known World. So if you learn "magical theory", you learn logic, rhetoric, mathematics, and science. This is simple to the Greeks learning The Four Elements and how they were "tied in" to other areas of schooling.