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Learning, thinking,
and creating.

Those three words cover just about all of my interests. I'm curious by nature and I get a lot of satisfaction out of learning about all sorts of subjects. It also matters to me to think critically, and to try to form as rational and nuanced a picture of the world as I can. But what I enjoy most is applying what I learn, whether that's writing an article or creating something like this website.

Lennart van Tuijl

About

Hi, I'm Lennart. Welcome to my corner of the internet.

Right now

  • Starting Biology & Medical Laboratory Research in February
  • Building LifeCore, a productivity app
  • Writing on Substack about rational thinking

DRAFT — replace with your own words. Everything on this site comes back to the same three steps, so it makes sense to say a bit more about each of them.

In February I start a degree in Biology and Medical Laboratory Research, and I want to continue into a master's in biology afterwards. Science is where my curiosity keeps landing, so it seemed the obvious place to get serious.

I build with AI tools. I know my way around computers and programming and I enjoy it, but I'm not a developer and won't pretend to be. Using AI means I can turn an idea into something that works, instead of waiting until I could write every line myself.

Floor-to-ceiling shelves of old leather-bound books with a wooden ladder leaning against them
01

Learning

DRAFT — I read widely and follow subjects wherever they lead: biology and medicine most of all, but also technology, history and anything that explains why the world looks the way it does. Science is the sharpest tool we have for finding out what is actually true.

ScienceBiologyTechnologyEducation
An open hand reaching up towards a lit light bulb floating against a pale sky
02

Thinking

DRAFT — Knowing something is not the same as having a view on it. I try to reason carefully, question what I take for granted, and end up with a picture of the world that is as rational and as nuanced as I can make it. Writing is how I do that work.

Critical thinkingPhilosophyRationalityPsychology
A desk at night with code open on a monitor and documentation on a laptop screen
03

Creating

DRAFT — This is the part I enjoy most: taking what I have learned and thought about and turning it into something real. Right now that is LifeCore and this website, and it is where my interest in entrepreneurship comes in.

BuildingEntrepreneurshipProductsDesign

Writing

Thinking out loud.

Rational Notes is where I work things out in writing: how we reason, where it tends to go wrong, and how to do a little better.

Read Rational Notes on Substack

Projects

What I've created.

Short list, honestly labelled. LifeCore is the real one — the rest is groundwork. As things get finished, they land here.

LifeCore

A productivity app I'm building

building

One place to plan your days, track habits and keep sight of longer-term goals — built because the tools I tried either did too little or asked too much upkeep. It's early: I'm designing and building it myself, with AI doing the heavy lifting on the code.

ProductivityWeb appSolo project
In progressNot public yet

Contact

Say hello,
I'm easy to reach.

If you're working on something in science, building a product, or writing about ideas — or you just want to ask something — I'd like to hear from you. I read everything, and I answer.