“Princess,” Twilight asked, her forehead creased once more in question: “do ponies have free will?”

Celestia regarded her student over the brim of her teacup. She swallowed and took a quiet, deep breath, before pasting a serene and practiced smile upon her lips, and setting down the cup. The porcelain clinked against its saucer, and even with millennia of practice Celestia had to quash her instinct to check for chips.

“My dear Twilight,” she began, her own brow furrowing in light-hearted curiosity, “whatever do you mean?”

Twilight was chewing nervously on her lip, her eyes darting around the room as if unable to settle on anything. She was twirling a piece of toast in her hornglow, a few small nibbles carved around its edges, untouched for several minutes now. Silly filly. It’ll get cold, you know.

“I was reading about some spells in the library the other day. Mind spells.” Twilight’s eyes had finally settled on the window, and they had almost glazed over as her mutterings caught up with her. They shot wide, her mouth moving faster than her mind could come up with words to say, and for a moment Celestia watched, an eyebrow raised in amusement, as her star pupil looked up at her in fear. Until, at last: “N-not books on how to do—on how to cast them, Princess. I wouldn’t look at that kind of book.”

This smile, less serene than the last, felt a little more comfortable on Celestia’s lips.

“They were just mentioned in a history book, Princess, and I went to look up more about their historical usage because of course I know that looking up the actual spells themselves is totally illegal not to mention completely irresponsible…” Twilight seemed to catch the amusement in her mentor’s eye and stopped herself mid-ramble, calming herself with a few very deliberate breaths. Celestia leaned forwards, taking the opportunity to steer the conversation off its tangential path.

“And what does this have to do with free will?”

“How do we know nopony’s controlling our minds right now, Princess? Surely, if they wanted to, they could make us think all our ideas and actions were our own choices. Even if, you know, they weren’t.”

A feeling of relief washed over Celestia: she released a breath she hadn’t even known she was holding, and felt her shoulders fall imperceptibly with the loosening of tension in her back. This wouldn’t be difficult at all.

“Twilight,” she began softly, “we have wards in place to detect those spells. Nopony is mind-controlling anypony now, and nopony ever will. Besides, if somepony were controlling your thoughts, would they really let you think that?”

Twilight’s mouth twisted in thought. Celestia rose from her seat, the gentle light from her horn reflecting as twinkling stars in her pupil’s mane and eyes, to rest a hoof on Twilight’s shoulder. It was almost routine, now, to calm small fillies from existential crises after their late-night studies—and after a thousand years, Celestia liked to think that her finely-adjusted routine worked.

“Trust me, Twilight,” she said, her smile patient and practiced, “nopony is controlling your thoughts.”

Twilight’s brow unfurrowed, and her lips relaxed into a smile as she turned back to her toast and took a bite, her worries forgotten, or perhaps reasoned away. And Celestia cut the light of her horn as Twilight grimaced at her toast, which flopped to her plate as the filly’s nose wrinkled in disgust.

“Princess, can we get some more toast?” Twilight asked. “Mine’s gone cold.”