Felix wasn't bored reading by himself, but soon, the girls' conversation shifted to him.
They began discussing the spell he had cast earlier and the way he had drawn his wand.
Hermione, who loved to get to the bottom of things, was the first to pose a question.
"What spell did you use just now?" she asked. "It sent that red-haired boy's wand flying in an instant."
"That was the Disarming Charm," Felix replied casually. "It's the most commonly used spell in wizarding duels. The incantation is 'Expelliarmus'."
"I know that one!" Marietta chimed in. "I remember it being mentioned in Defence Against the Dark Arts, but Professor Quirrell said we wouldn't learn it until the higher years."
"You can actually use such a complex spell! How did you manage that?" Given that Felix, like her, was Muggle-raised, his ability to use such a spell was clearly a blow to Hermione. She eagerly pressed him for the secret.
"Actually—" Felix explained, "this spell isn't complex. In fact, among all the spells that can be used for direct confrontation, the Disarming Charm is one of the simplest. Although it doesn't have a very powerful damaging effect and is easily blocked by various counter-charms, it has one advantage that other spells can't match."
"What advantage is that?" Hermione asked, rather impatiently.
"It is the duelling spell with the shortest incantation, the one that can be cast the fastest. Using this spell often allows you to seize the initiative in a magical duel."
Hearing this explanation, Cho Chang and Marietta both nodded in sudden understanding, impressed by Felix's extensive knowledge.
Hermione, however, remained unconvinced. She challenged him, "I've never read that conclusion in any book – that 'Expelliarmus' has the shortest incantation. Which book did you see that in? I haven't seen any mention of the length of different spell incantations in any spellbook."
"It's my own conclusion. I reached it after comparing several relatively simple duelling spells like the Stunning Spell, the Impediment Jinx, the Full Body-Bind Curse, and the Dancing Feet Spell," Felix answered.
"But, if it's not written in the books, how can you guarantee that your conclusion is correct? You know, these books were written by the greatest wizards. Even they didn't say that. On what grounds do you believe you're right?"
She really is a proud child, Felix thought, unwilling to admit defeat at any turn. Let me teach her a little something.
With this in mind, Felix adopted a serious tone and began to critique Hermione.
"Miss Hermione Granger, I presume that since being accepted to Hogwarts, you haven't been keeping up with your Muggle science studies, have you?"
"N-no... that's right. But what does this have to do with Muggle science?" Hermione retorted, her face flushing.
"It has a great deal to do with it. Muggle science, while lacking the convenience and wonder of magic, offers methods of logic and problem investigation that are very much worth learning. They can even serve as a reference when studying magic."
"For instance, to study the length of incantations, I simply need to maintain my magical power and concentration at a consistent, abundant level, use the same volume and speed of speech to clearly and completely cast different spells, and then record the time for each. This way, I can roughly compare the lengths of the incantations – this is what's known in science as the controlled variable method," Felix explained earnestly.
"Finally—" he concluded, "the spirit of science tells us that truth can only be derived through practice and experimentation; blindly trusting authority is an inadvisable approach. Even in the scientific world, the theories of great figures like Newton have been proven not to be absolute truths in the modern era and have limitations in many aspects. So, on what basis do you assume that the wizards who wrote these magical textbooks are entirely correct? After all, magic, in terms of rigor, does not quite measure up to science."
"If the words of these predecessors were entirely correct, then how would new spells ever be created? After all, the books of these predecessors don't mention those new spells. If we follow your line of thinking, the entire wizarding world would cease to progress."
This explanation left Marietta, who came from a wizarding family, completely bewildered – in truth, many wizards didn't possess strong logical reasoning skills. However, Hermione Granger, from a Muggle family, and Cho Chang, who had spent a long time in the Muggle world, managed to grasp what Felix was saying.
"This is the first time I've ever heard such an idea," Cho said, looking at her fellow kinsman with admiration. "Using scientific methods to study magic – you truly are a genius."
Hermione, on the other hand, looked as if she were on the verge of tears.
She had always prided herself on her intelligence and had been reluctant to concede to Felix. Yet, Felix's theory was so logical and reasonable that she couldn't refute it. This placed her in an awkward position: she wanted to argue but was speechless; she wanted to apologize but found it hard to swallow her pride.
Ultimately, she chose to apologize.
"S-sorry," she whispered. "I admit I was wrong. Please forgive me..."
But before she could finish, she burst into tears and ran out of the compartment.