A/N: My gratitude to Luna for the long-distance beta; to Anastasia, as always, for inspiring courage; to a post-structuralist named Lyotard for ruining several weeks of my life in grad school; and to Ari!Mom, because of whom I survived Ophelia with my love for math intact.
Unthinkable
But Severus' eyes were alive with the glimmer of an idea so absolute, so wrong, so perfect, that he knew he was right.
Turning toward the archway, he called, "Phineas!"
Dimly Hermione heard Phineas Nigellus' voice echo in the hall.
"We need to speak to Dumbledore."
-------------------------
"Severus, what is it?" Hermione asked, rising to join him as he strode toward the hall.
"It's unthinkable, Hermione," he said, a delighted and undeniably malicious grin spreading on his face.
This was so unlike any answer she had expected that she stopped short for a moment before increasing her pace.
He swirled to a stop in front of Mrs. Black's portrait, where the witch was uncharacteristically silent, her expression one of listening for something that wasn't really a sound.
"He's coming," she said, and left her frame.
Dumbledore appeared a moment later, without Phineas Nigellus. "Ah, Severus. Miss Granger. Good evening," he said pleasantly, as though they'd just encountered each other unexpectedly whilst on an evening stroll.
"Headmaster," Severus inclined his head, as Hermione said, "Good evening, sir."
"The good Phineas Nigellus has stayed at Hogwarts," Dumbledore continued calmly, "lest my presence be required there."
From this they understood that Professor McGonagall was not the only Order member currently at the castle, and they nodded.
Dumbledore turned to Severus expectantly.
"Headmaster," Severus began, his eyes very nearly sparkling, "I have missed our debates on the merits of order and chaos."
Dumbledore nodded, the quality of his attention changing as he seemed to notice the light in Severus' eyes. "As have I, Severus; as have I."
"If we could perhaps continue our discussion of conditionals versus imperatives, I believe it might prove to be most… useful."
Hermione blinked. Grammar? What has grammar to do with anything?
But Dumbledore smiled as if nothing would please him more, and he settled his robes around himself comfortably. "The conditional is a tense; the imperative, a mood. That is where we were, I believe?"
"Indeed."
Hermione gaped as the kitchen door swung open and two chairs appeared in the hallway.
Severus gestured for her to sit, but did not take his eyes off of the portrait. "I believe, sir, that I have recently begun to see the merits of your position regarding the permeability of that distinction, and would like to test my thinking."
"Of course, Severus. You refer to my contention that the line between 'must' and 'should' is entirely illusory, I believe?"
Severus nodded.
Hermione could have sworn that the headmaster was beginning to beam. Paint cannot beam. It just can't… She rubbed her hand over her face. Of course it could. It was doing just that, right in front of her.
"Sir, if one were to propose the inverse of your argument – that the distinction between 'must not' and 'should not' not only exists, but is, in fact, impermeable - would you agree?"
Dumbledore nodded, slowly, his eyes alight with speculative interest.
"And if one were to further define that inverse argument by placing it within context – which is, of course, always changing – would it – would it then be accurate, Albus," Severus leaned closer to the portrait in his chair, his excitement palpable. "Would it then be accurate to say that the distinction between 'must not' and 'should not' exists, and is definite, but that at any given moment the distinction is so subjective that it is nearly useless?"
Dumbledore looked so very pleased with this baffling question that Hermione could have sworn that Severus' asking that specific question was what the former headmaster had been seeing in the Mirror of Erised for years.
Severus leaned back in his chair and crossed his arms, his eyes proud.
Dumbledore continued to beam at him.
And Hermione was completely confused, and beyond irritated by both of them. "Excuse me," she said, in as respectful a tone as she could muster, "but would one of you please explain what all that was about?"
Dumbledore gestured for Severus to do the honors.
Severus turned his head toward Hermione with a smile that was simultaneously gentle and predatory. "It means, Hermione, that 'taboo' - or 'thou shalt not' - however absolute, is merely a social construct, subject to change depending on context."
He waited for a moment, and, when she did not reply, he continued, "It means that we're going to divide by zero."
She blinked.
Dumbledore laughed. "Well done, Severus, well done indeed."
Severus glanced at him, pleased, but turned his gaze almost immediately back to Hermione.
She blinked again.
Dumbledore watched them for a moment, a delighted smile on his face, then said, "As you doubtless have much explaining to do, Severus, I believe I will beg my leave of you both and return to Hogwarts. Good evening, Miss Granger." He nodded at both of them, and the frame was empty.
Hermione was blinking rapidly. "We're going to… what?"
"Really, Miss Granger," Severus began, in a tone so light she was alarmed.
Teasing? Him? "Miss Granger?" Hermione said, astonished.
Whatever she was going to say next was interrupted by his laugh. "Please – forgive me, Hermione, but it is so rare to see you flummoxed that you will forgive my indulging my enjoyment."
"Yes, because letting you have your way always works so well for me," she muttered, then blushed. "Um… what I meant was... "
Severus laughed again, and reached for her hand.
"I don't enjoy being confused," she said irritably. "And I particularly don't enjoy being laughed at when I am. 'Miss Granger.' Honestly, Severus."
"Imagine my surprise," he said softly, his tone returning to something more usual, but his dark eyes still gleaming with amusement. An amusement that was tingeing with something else, something Hermione found rather distracting.
Withdrawing her hand, she folded her arms. "Explain. Please."
"Very well," he said amiably, leaning back again, his legs stretched out before him as if he had unlimited leisure. "Basic Muggle mathematics."
Mind completely spinning, Hermione nodded for him to continue.
"Why can one not divide by zero?"
"Because the answer is undefined," she replied promptly, reciting the answer every Muggle schoolchild knew by heart.
His eyes glittered, a barely restrained riot of deviant wisdom. "Think, Hermione, and try it again. Why can one not divide by zero?"
She frowned at him. "Because dividing by zero makes no sense. You cannot evenly portion out a whole into equal parts if the parts themselves are not parts, but nothing."
He shook his head, and the untamed amusement in his eyes grew wilder, deepened into something untranslatable.
His expression rather reminded her of Crookshanks, and she tossed her hair. "Severus, please. What are you on about?"
With a patience so infinite it made a delicate mockery of itself, he repeated the question. "Why can you not divide by zero?"
"Because," she said, exasperated, "there's no point!"
And then she froze.
"It's the wrong question, isn't it," she said, an intensity born in her eyes, quickly growing to match his. "You can divide by zero, you just… don't. Unless - "
" - unless the circumstances demand it - "
" - and you don't expect a rational answer - "
" - and you require that the answer not make sense - "
" - and the outcome you want is for the answer to be undefined," Hermione breathed, her voice barely above a whisper.
"Unthinkable, isn't it." Severus' eyebrow arched over his darkly sparkling eyes.
They both smiled.
Definitely not nice.
So far beyond "not nice," in fact, that - had they but seen it - every Gringotts goblin would instantly have deserted his post and caught the first flying carpet out of the country.
And goblins never leave their gold.
