Isotope opened his door to find his old mentor standing there. “Wood Phase? Golly, what are you doing out this late?”
The older stallion seethed. He wore neither coat nor scarf, despite the weather. His mane was unkempt, his fetlocks mussed, his eyes wild. He stood on Isotope's doorstep amid the gathering snow as wind whipped through the dark night.
Isotope tried again. “By the Princess, old chap, what happened to you? Nopony knew where to find you.”
“What happened to me? You want to know what happened to me?” Isotope nodded. “The truth! That’s what happened to me.”
“I… I don't understand. Look, please come out of the cold.”
“I can’t!” shouted his mentor. “Don't you see? I can never escape it again. And it's all your fault.”
“My fault? Dear fellow, please explain. I've never harmed you in any way, have I? On the contrary, I admire you. After all, you taught me everything I know. You taught me to always search for the truth.”
The older stallion barked a short, bitter laugh. “I did, didn’t I? The truth…” He turned, exposing his flank in the doorway. “What do you see here? This cutie mark, what do you see?”
“I see... your cutie mark. The five elements, in a cycle of overcoming and mutual virtue. Conflict and cooperation in balance.”
“That's right. Five elements. Not sixty-three.”
“Oh… Oh, I see. Is that what this is—”
“My whole life!” shouted Wood Phase. “My destiny. My career. Dedicated to a lie!”
“Really, that wasn't—”
“A lie! A lie that was just exposed by you. Or will be in a few days when everypony reads that accursed paper of yours. A single dream is all it took for you to reveal the sand on which my castle stood.”
“Do you want me to recant? Is that it?” asked Isotope. “My paper surely hasn’t reached the publishers yet, if we run now I believe we can intercept it.”
“No…” The older stallion’s legs gave way and he slumped on his student's doorstep. “No, no, there’s no point. Somepony else will discover the same thing eventually. And even if they never do, I would still know. I can never stand before my students with the same pride as before. Not when I’m branded with a lie.”
Isotope knelt down to Wood Phase's level. “Come in and have a brandy, old chap. I’m sure we can sort this out.”
Wood Phase nodded, sighed, and allowed himself to be led to a comfortable chair near the fire. Isotope poured a pair of generous brandies, levitated them over and sat down next to him. The older professor cradled his glass in both hooves, hunched over it.
“I owe it all to you,” said Isotope. “You taught me to see the patterns in reality. You taught me to look at the evidence rather than my own assumptions. You taught me to look for the truth, in the face of a world that doesn't want me to. This is your triumph as much as it is mine.”
“I know, I know,” said Wood Phase. “And I meant every word of it. I tried to get all my students to look for the truth, even if you were always my most promising. I just… never expected it to come back and bite me on the rump like this.”
Isotope’s eyes drifted down to his mentor’s cutie mark, a pentagon with five symbols in circles and ten arrows arranged between them in circular symmetry.
“I still remember learning about the history of the five elements. How ponies only thought of the world in terms of angry spirits or magic spells, but never thought of what objects were made of – until Quince observed the interactions of materials and deduced the elements from which all things are made.”
“But it wasn’t true,” muttered Wood Phase. “The world isn't made of fire and air and metal. She made a mistake.”
“Did she? Earth pony culture thrived in the centuries that followed. Working with the five elements allowed them to smelt new metals, harness the power of the elements, treat diseases they couldn't have before. Only the sacking of Terrina by Commander Bluewing stopped them.
“A theory may not be the whole and final description. But it doesn’t need to be if it gives you power over the world. A theory should usefully describe the world in a way that allows you to make testable predictions.”
Wood Phase stared down at his brandy, warm colours from the fire glinting through the cut glass. A faint smile touched his lips. “First year, third month. I didn't think you were listening. I thought you were too busy passing romantic missives to Perrivale.”
“I wasn't,” admitted Isotope. “But Perrivale took excellent notes. I caught up later.” He glanced at the wooden stairs, flickers of firelight casing them in warm colours. “Don't tell my wife that, please? She and Perrivale are still friends. I'd hate to upset that.”
“Of course not,” said Wood Phase. He took a slow breath. “It doesn't change anything, though. Useful or not, the five elements theory isn't true.”
“And you're certain my new periodic table is?”
“I saw the draft of your paper, Isotope. It explains everything we've seen in our experiments, even things I hadn't considered. And it predicts the existence of other elements we've yet to find.”
“But I hear Professor Valance over in Fillydelphia has been working on a periodic table of elements very similar to mine, but which places Phlogiston and Celestium on the top row rather than the left column.”
“He has? I didn't think the old fart had an original idea in him.”
“That's actually why I rushed my paper to print, before he could preempt it. But it may yet prove to be a better description than my own. And in another century or six, who knows? Another revolution may upset all our apple carts.”
“You make it sound like you don't believe in your own theory.”
“As the ultimate truth, forever? No. There are things my theory doesn't yet explain, and while it’s sure to be refined, no theory lasts forever. A good theory can still push the bounds of pony knowledge.”
Wood Phase twisted to look down at his flank. “And you think the pony on the street will understand that distinction? Surely they'll just see a symbol of a defunct theory, marking me as belonging to the past.”
“You give them too much credit. I doubt most ponies will know the difference, even in this town. And the minority that do will know you by your reputation. You've taught a lot of young stallions and mares. Many of them will remember your lessons as I do.”
Wood Phase drained the last of his brandy and set it down on the low wooden table that sat before the fire. He had to nudge a cluster of apparatus out the way to do so, and frowned as he looked at it.
“What’s that stuff about? Are you starting a miniature dragon hoard?”
A small square of gold leaf was suspended in an upright wooden frame. A pair of crystals sat nearby, one dark grey and one light green with a thin hole drilled through the middle. A movable frame contained what looked like a canvas.
“Oh, something one of my own students has been working on. The hematite gives off magical radiation when stimulated, which she focused onto the foil then used the fluorescent screen to see how it’s scattered.”
“Fairly predictable, I’d have thought. It’ll blur out a little because of the magical charge.”
“That’s what we both expected. Turns out, though, some of it gets reflected back.”
Wood Phase’s frown deepened. “That’s odd. I wonder why. Mistake in the experiment?”
“It could be. You have to minimise your magic around it, the screen picks up everything. She did it a bunch of times though, so she’s fairly sure it’s real. I don’t suppose you have any thoughts why it would do that? Because I'm stumped, really.”
Wood Phase scrunched up his greying muzzle. “Well, I suppose I have one idea. It's a bit unconventional, though…”