#scholar writes

In Tevinter, during the height of the Towers Age, a Magister named Allineas devised the theory of Arcanist Derangement.  The talent of all mages - that is to say, the magic itself - runs like a river.  Properly forded by training the river ‘returns to the ocean,’ and is channelled properly through the vessel, out into the world where it is largely drawn back to the Fade, allowing mages to cast spells as we know them.  Those who have not received this training, however, cannot on their own learn to channel this magic in the same way.  But the river still must flow, straining against whatever barriers of willpower a mage should try to hold in order to stop themselves burning down houses unintentionally when emotions run high.  Those individuals who manage to survive, whom we term Hedge Mages, are those who have learnt to live with the way their magic expresses itself, even turning it to their advantage.  Some, like the Qunari Saarebas, may even express magic in dangerous and spectacular ways, as it rushes forth and is expressed in the only way the Saarebas can control it without destroying themselves.  Their magic, therefore, is solely destructive.  It is important to note that some cultures, such as the Chasind, Avvar and the Dalish do not experience this, having their own cultural traditions in the training of mages.  A Dalish mage, therefore, might master the way of the Knight Enchanter in a way a Saarebas never could. THESE ‘CULTURAL TRADITIONS’ NOT RELEVANT 

Prior to the establishment of the circles, then, magical talent expressed itself in many ways.  Not always randomly, sometimes mages were ‘trained’ in ancient traditions and had abilities no circle mage could ever hope to master, but without modern training methods discovered, this way of learning and practising magic would always be especially risky.  Indeed, the term ‘arcanist derangement’ expresses in its name the effects of such channelling: Very often unpredictable, practitioners were chaotic and wild with their talents.  Allineas writes from experience of mages communing with spirits and being lured down ‘darker paths,’ < GIVE EXAMPLES! with many eventually succumbing to madness.  He makes it clear that many of these individuals did not live long lives. 

In addition, those who have forced a path for their magic, after a certain amount of time doing this, can no longer relearn the proper way to ford the river.  They are no longer able to cast spells, and can only direct magic as they have learnt themselves.  Therefore, Circle training is paramount to both the survival and sanity of mages everywhere, as we pass on the knowledge of how to safely draw the magic through us that is in turn drawn to us naturally from the Fade.

✓ GOOD ANSWER.  DON’T FORGET TO USE CITATIONS WHEN QUOTING THE WORK OF OTHERS. 

-- From a marked essay by a young Circle Mage, concerning the question, ‘Why are the Circles necessary to the survival of mages?’  Recovered from the Tower library of Ostwick, after it fell in 9:41 Dragon.