The initiates stood quietly in a row along the arbor loggia, watching the long, deep, marble-lined trench ahead of them flash with fire. The air above it vibrated with the waves of heat. Though each student kept his or her face sturdy and emotionless, as a true Psijic should, their terror was nearly as palpable as the heat. Sotha Sil closed his eyes and uttered the charm of fire resistance. Slowly, he walked across the basin of leaping flames, climbing to the other side, unscathed. Not even his white robe had been burned.
"The charm is intensified by the energy you bring to it, by your own skills, just as all spells are," he said. "Your imagination and your willpower are the keys. There is no need for a spell to give you a resistance to air, or a resistance to flowers, and after you cast the charm, you must forget there is even a need for a spell to give you resistance to fire. Do not confuse what I am saying: resistance is not about ignoring the fire's reality. You will feel the substance of flame, the texture of it, its hunger, and even the heat of it, but you will know that it will not hurt or injure you."
Sotha Sil turned back to the students, his voice flat. "Fear does not break spells, but doubt and incompetence are the great enemies of any spellcaster. Master Welleg, you will pack your bags. I'll arrange for a boat to bring you to the mainland tomorrow morning."
The School of Mysticism by its very nature forces the practitioner to divorce his mind from logic, to embrace a temporary sort of insanity, which one might argue is very like corrupting one's soul.
It also kind of seems like Neo learning to bend reality through will in the Matrix. He just needs to believe he can jump from one roof to the next without hesitation :shrug: And apparently imagination is as essential as willpower.
The second quote might offer insight into how the silence spell works... maybe?