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“I want a notebook. A paper one. With lines.”

Diwa drew out his laptop, lid angled towards Cassian within seconds. “Can I show you something?”

Cassian pulled the blanket higher and looked at the screen. It was dark-themed, covered in text, with small interconnected boxes linked by fine grey lines that reminded him of the diagrams in his Entry Level 3 science workbook. Except instead of the water cycle or the parts of a cell, the boxes had labels like Tala — feeding log and Tala — sleep regressions and Tala — developmental milestones (gross motor).

“This is my Obsidian vault,” Diwa said. “It’s my personal knowledge management system. Everything I think, everything I read, everything I need to remember, it all lives here. All connected with each other.”

He clicked on one of the boxes, and a page opened that contained a single paragraph about Tala’s reaction to puréed sweet potato, cross-referenced to three other pages about texture preferences, allergen introduction timelines, and something called a sensory processing note.

“It’s all about keeping atomic notes,” Diwa continued, leaning closer to the screen. “Each idea gets its own page. One thought, one note. And then you link them together, so the connections between your ideas become visible over time. It’s like…imagine your brain, but searchable.”

“I search my brain by thinking, Diwa,” Cassian said.

“I’ve hooked the whole vault up to a locally hosted language model. It reads everything I’ve written, indexes the semantic relationships, and surfaces connections I wouldn’t have found on my own. Look. This is the Tala vault. Every observation I’ve made since she was born, tagged by category, date-stamped, and backlinked to related entries. If I want to know whether her Thursday sleep regression correlates with a feeding pattern change, I can trace the links in seconds. And the daily notes aggregate into weekly summaries automatically.”

The screen now showed a web of interconnected nodes so dense that it looked like a photograph of the night sky taken through a very expensive telescope. Each node was a thought Diwa had catalogued about his infant daughter, and there were thousands of them.

“Diwa, I really just want a notebook.”

“And the beautiful thing is, it all compounds. The more information you add, the more connections emerge, and you start to see patterns you never would have noticed otherwise. Your notebook, the one with the rules about alphas. Imagine if every rule was its own atomic note, and you could see which rules connected to which experiences, and trace the evolution of your thinking across—”

Cassian reached across and closed Diwa’s laptop.

“Diwa, my mind says no to this.” He patted the closed lid. “Can you please just give me one of your fancy notebooks?”

Diwa looked at his laptop like his last ally had just defected. “I’ve been trying to get Colin to use this for a shared family log for six months, Cass. I thought if you were on board, he’d have to cave.”

“Colin will never cave, Diwa. You know that.”

“I know.” Diwa picked up his laptop and tucked it under his arm. “I have Leuchtturm1917s in the study. Do you want dotted or ruled?”

Cassian chose the dotted rule.

Diwa returned with a charcoal notebook, its pages full of tiny dots arranged in a grid. He set a pen on the cushion beside Cassian.

“This,” Diwa said, “is a Fisher Space Pen. It uses pressurised nitrogen to force ink towards the nib, which means it can write in zero gravity, at any angle, underwater, and in temperatures from minus thirty to one hundred and twenty degrees Celsius. NASA started using them in the nineteen-sixties.”

Cassian picked it up. It was silver and heavier than it looked. “This pen works underwater?”

“Flawlessly.”

Cassian clicked the pen twice, watching the nib appear and retract. “Diwa, can the Leuchtturm be written on underwater?”

“No.”

“So what’s the point of having a pen that can write underwater if I don’t have paper that can be written on underwater?”

Diwa stood. Cassian had learned this escape manoeuvre from watching Colin deploy it: ask Diwa a question his enormous mind hadn’t considered, and watch him spiral into a forty-eight-hour research fixation.

“I need to check on Tala’s—” He was already halfway to the door. “Colin asked me to—”

The door clicked shut behind him, and his footsteps took the stairs two at a time.

Left in peace, Cassian clicked the space pen, opened the Leuchtturm to its first dotted page, and wrote at the top in his best handwriting, the letters still uneven and too large, but legible, which they hadn’t been six months ago:

THINGS I KNOW

I am working on knowing my own mind.