Tenure

The Philosopher came again to the worn steps curving up Academy Hill. The slate walk stretched away before her, circling the school. She sometimes walked this path for hours, puzzling out problems.

"Hey," the Artisan shouted, "Wait up."

"Well, keep up," the Philosopher grumbled. A tinkerer, was the Artisan. A flipper of rocks, with no respect for deep thought.

He trotted up, clutching a silver cylinder. "I needed to make sure I dialed it in right. This is a precision instrument."

The Philosopher glanced at the contraption. "It's a big red button glued to a tin can."

"That's a skirted potentiometer knob," The Artisan said. He shrugged. "Yeah, it's ugly, a shakedown cruise. But it works. It's a genuine time machine."

Just like that. The Philosopher considered the statement as they passed the Hall of Reason.

"That is unlikely," she said at last.

The Artisan smiled. "Think so? You're great at dismembering the universe, but you couldn't assemble a tricycle."

"And how does this time mach-- time button operate?"

"You set the knob once and you go into the past. You tune it again, back to its original position, and you go forward to where you started."

"I see. What makes you think this magic time button works?"

"Potentiometer knob. Skirted potentiometer knob. I tested it! Just a little while ago, behind you. Went back one hour."

The Philosopher frowned. "The, umm, hypothesis of time travel contradicts a linear progression of cause and effect."

To her surprise, the Artisan understood the paradoxes. As they walked past the dorms they debated murdered grandfathers and multiple timelines. They pondered time travelers who could only observe the past, or who changed time so it became the history they knew.

At last the Philosopher asked, "What if time forms a loop from the moment of departure to the moment of arrival? What if history wraps around itself, if time's arrow chases its own tail?"

Her companion lagged behind, adjusting his precision instrument, his tin can. She came again to the worn steps curving up Academy Hill.

"In that case," she said, "the first time traveler would be the last." The slate walk stretched away before her, circling the school.

"Hey," the Artisan shouted, "Wait up."