The Senior Common Room at St Anselm's had settled into one of those contemplative silences in which the rain at the windows seemed to possess stronger opinions than the faculty.
Professor Quillibrace sat beside the fire.
Miss Elowen Stray was making notes with increasing concentration.
Mr Blottisham entered looking exceptionally pleased.
Quillibrace looked up.
Then narrowed his eyes.
"You appear encouraged."
"I am."
"Oh dear."
Blottisham sat down triumphantly.
"I've solved the matter."
Elowen looked cautious.
"Reality again?"
"No."
Quillibrace looked relieved.
"Good."
"A smaller problem."
Quillibrace became suspicious again.
"Which smaller problem?"
"Gravity."
Long silence.
Quillibrace closed his eyes briefly.
"My dear fellow..."
"What?"
"...we only recently dismantled gravity."
Blottisham waved dismissively.
"Yes, yes. But now I understand it."
"Oh no."
Blottisham leaned forward enthusiastically.
"I've been thinking about Einstein's elevator."
Quillibrace looked suddenly wary.
"Have you indeed."
"Certainly."
He spread his hands.
"If I stand in a sealed elevator and feel myself pressed against the floor, either gravity is pulling me downward or the elevator is accelerating upward."
"Yes."
"And Einstein says I cannot tell which."
"Yes."
Blottisham sat back smiling.
"Simple."
Silence.
Elowen looked up.
"Simple?"
"Of course."
He nodded confidently.
"The explanation is obvious."
Quillibrace stared at him.
"My dear Mr Blottisham..."
"Yes?"
"...I have developed a growing fear of that phrase."
Blottisham folded his arms.
"Clearly one of the two situations must be real."
Silence.
Quillibrace looked toward the ceiling.
Elowen covered her mouth.
After a while Quillibrace spoke quietly.
"Real."
"Yes."
"The genuine situation."
"Precisely."
"The one secretly hiding beneath appearances."
"Exactly."
Long silence.
"My dear fellow," said Quillibrace gently, "the equivalence principle exists almost entirely to destroy that sentence."
Blottisham blinked.
"I don't follow."
Quillibrace stood and wandered toward the windows.
"The classical imagination depends upon sharp distinctions."
He counted on his fingers.
"Gravity is gravity."
"Yes."
"Acceleration is acceleration."
"Yes."
"Inertia is inertia."
"Yes."
"And each possesses some stable identity independently of context."
"Precisely."
Quillibrace turned.
"And Einstein quietly removes the floor from beneath all of them."
Blottisham looked uneasy.
"But surely if I inspect things carefully enough—"
"Ah."
Quillibrace raised a finger.
"There it is."
"There what is?"
"The final refuge."
Elowen looked thoughtful.
"The assumption that sufficiently local examination eventually reveals reality as it truly is."
Quillibrace pointed approvingly.
"Very good."
Blottisham frowned.
"But isn't that reasonable?"
Quillibrace sat down again.
"Ordinarily, yes."
"Excellent."
"But unfortunately reality appears not to have consulted us."
Silence.
Quillibrace continued.
"The astonishing feature of the equivalence principle is that local structure underdetermines interpretation."
Blottisham blinked.
"Meaning?"
"Meaning that what you encounter locally does not uniquely tell you what you are."
Silence.
Blottisham stared.
Then stared harder.
Elowen leaned forward.
"So acceleration and gravitation become locally indistinguishable."
"Exactly."
"And therefore their apparent distinction cannot arise from local structure alone."
"Precisely."
Blottisham looked alarmed.
"So gravity disappears?"
Quillibrace nodded.
"Locally, yes."
"That seems extremely suspicious."
"Does it?"
"A proper force should remain where one left it."
Quillibrace looked at him.
"My dear Mr Blottisham..."
"Yes?"
"...you've accidentally rediscovered why Einstein found this so remarkable."
Blottisham sat very still.
"So if I examine only what happens inside the elevator..."
"Yes?"
"...I cannot determine some final hidden truth about what is occurring."
"No."
"Because the local situation participates in multiple larger relational organisations."
"No less than exactly so."
Silence.
Blottisham stared into the fire.
"My God."
After some time he spoke quietly.
"So reality isn't locally self-explanatory."
"No."
"And local appearance carries no final ontological authority."
"No."
"And things only become intelligible through broader transformational relations."
Quillibrace slowly put down his teacup.
"My dear Mr Blottisham..."
"Yes?"
"...you are becoming increasingly dangerous."
Rain tapped softly against the windows.
Nobody spoke for a while.
Then Blottisham frowned.
"Though one issue remains."
Quillibrace looked exhausted already.
"Naturally."
"If local phenomena cannot determine their own interpretation..."
"Yes?"
"...does this explain why Cook's puddings always seem either impossibly heavy or mysteriously light depending upon where one sits in the dining hall?"
Quillibrace looked toward the ceiling.
"My dear fellow," he said quietly, "I have long suspected locally variable dessert geometry."