"How do I know?" Septimus repeated with a sly smile. "Oh, I have my sources. I believe that's the saying, isn't it?" Of course, there were those on staff who were aware of Septimus'.... "tenant"... but it was not a fact he advertised to all and sundry. Even in this day and age, tell a person you have a demon in your head, and they're prone to look at you askance, make assumptions, and then come the accusations and the holy water, and it all goes downhill from there. And, despite Murmur's power, they were not without their vulnerabilities.
"It's a sensible attitude you have," Septimus continued, declining to answer the question in any real sense. "Laying on hands is all well and good, but don't underestimate the power of science, boy. Too many do. Arrogance; that's all it is. Why, if you had seen how disinfectant changed the world!"
Regardless of his own magical ability, Septimus was, at heart, a skeptic. He liked things to have tangible, quantifiable, and above all predictable causes and effects. For him, "It's magic" had never been a satisfactory explanation for anything. For that, other witches tended to view him with either condescending pity or else offended hostility, whereas the ungifted called him unorthodox to his face and unstable behind his back.