When Brian saw Norberta, now as large as a cabinet and under a Fire-Extinguishing Charm, stretching her neck but failing to breathe fire, he realized something-Mr. Filch was a Squib, and he did not know that the Little Dragon and Stone Soldier were, in truth, "not magic."
"She can breathe fire already?" Brian stroked Norberta's rough wings. The dragon was busy dealing with two trembling mice and did not mind being rubbed a few times.
"Yes, she burned off one of Silvanus's arms in a flash yesterday."
Hagrid said happily,
"Some dragons take ages and ages to learn to breathe fire. Some never learn at all, just like Squibs among wizards."
Squibs, wizards who could not use magic-or rather, Muggles who knew magic existed but could not use it-were like withered, yellow plants growing in cracks. There were few of them, and they went unnoticed. Even if someone observant spotted them, their fate was either to be pulled out or left alone, their lives in the hands of chance.
Naturally, such plants were far more likely to grow crooked than those raised in flowerpots.
Perhaps being a Squib was precisely why Mr. Filch was always saying things like, "In the old days, unrepentant students like you would have been strung up and whipped."
At that thought, Brian suddenly felt a little sorry for Filch. Yet the truth was that, with his considerable talent for magic, he could not truly put himself in Filch's shoes at all. He hurriedly took a drink, dispelling that arrogant thought and bringing his wandering mind a little closer to practical matters.
Rather than consider how wizards viewed Squibs, it was more practical to first consider how they viewed Muggles-at least for a Muggle Studies professor like him.
Brian kept feeling that something was wrong with