What Edwin was referring to was the "School Barrier," an issue that had plagued the Wizard World for centuries.
A Wizard proficient in the Moldable Energy School would find it nearly impossible to also master the opposing Illusion Series and Necromancy Series.
A master of the Transformation Series, in turn, would have no aptitude for the Defense Series and Prophetic Series.
This wasn't a simple knowledge gap or a matter of sectarianism.
Rather, it was a case of matter determining consciousness.
When a Wizard delved deep into learning and mastering the Magic of a certain school, it meant that their individual thought patterns, Mental Force Field, and even the subtle material structure of their soul would be reshaped by that school's core principles, forming an acquired "Thought Steel Seal."
This specialized cognitive structure naturally repelled the principles of other schools, creating an almost insurmountable Knowledge Barrier.
