Mathias Celis

The through-line

Across nearly every post, Mathias Celis returns to one preoccupation: the human cost of unmanaged email and the decision fatigue it creates. He frames the inbox not as a productivity nuisance but as something closer to a cognitive hazard, quoting a criminal lawyer's line that "Mails zijn een beetje de dood van de geest van de mens" and building a whole product, Pidgy, around the idea that speed is the wrong fix for the problem . Over time the framing shifts from diagnosis to prescription: early posts describe the psychological mechanics of why inboxes trap people , later posts argue that most AI tools attack the wrong symptom , and the most recent posts show him testing and defending an actual product built on that theory .

On email as unresolved decisions

Celis's core claim is that every email is an open decision disguised as a message. "Elke mail die binnenkomt [is] een openstaande beslissing met een aanhef en een afsluitzin errond," he writes, and the real question buried in it is always "Verdient dit iets van mij, ja of nee" . He ties this to research suggesting unresolved items are cognitively sticky: "De mails die je leest zonder te beslissen, blijven plakken" . Returning from time off makes the pattern visible: "400 emails, and the first three hours of your week gone... None of that is work. That's finding out what the work is, and it's a miserable way to spend the first morning back" . Even holiday recovery gets colonized by this dread, since "Holiday wellbeing peaks around day eight" and then slides as the imagined pile grows .

On treating the disease, not the symptom

Celis is explicit that faster email tools solve the wrong problem. "Most AI email tools just help you answer email faster. That is a faster belt on the same treadmill. You are still running. You have just been handed nicer shoes" . His alternative framing: "The goal is to spend less of your life in there at all, so your real work gets the good hours instead of the leftovers" . He applies the same logic to why people resist switching tools even when they know their current system is broken, invoking "the sunk cost fallacy" to explain why "professionals stick with imperfect tools" and why "the cost of changing is paid today, while the benefit lives somewhere in a vague potential future" .

On lists versus plans

A related theme is his insistence that intention without a time and place doesn't produce action. "My to-do list used to be a wish list... The task never got easier. It just got older," he writes, before drawing the operating principle: "A to-do list makes you decide what to do every time you open it. A calendar already decided. You just show up" . This becomes a design principle for Pidgy: "turning the emails that pile up into tasks that actually have a time next to them" .

On heat and cognition

In two posts he extends the same cognitive-load lens to physical environment. Heatwaves, he argues, turn "kenniswerkers... in heethoofden," and he traces this to the brain: "Aanhoudende hitte tast namelijk de werking van onze prefrontale cortex aan, het deel waarmee we zouden merken dat we slechter beslissen" . He also notes an aging-related detail behind the claim, that older people's internal warning systems are blunted, "Zijn waarschuwingssysteem gaat simpelweg niet meer af" , reinforcing his broader interest in how the brain's decision-making machinery degrades under strain.

From the stage

On the "Gele Auto's Tellen" interview, Celis describes something the written posts never touch: his personal coping mechanism for cognitive overload while juggling a PhD and multiple startups, which he calls "cleanup rage," paired with self-care rituals, and he stresses deliberately surrounding himself with people who challenge his ideas and hold him accountable ¹⁶. On the audit-profession podcast, he frames the invisibility of the auditor's work as an aspiration problem: "you can't aspire to something you never see," calling audit "the kiwi of professions" , a comparison not developed elsewhere in his written output.

Takeaways

• Treat every incoming email as a pending yes/no decision rather than something to merely read, since unread-but-undecided items stay cognitively "stuck" .
• Don't judge an email tool by how fast it lets you reply; judge it by how much of your life it removes from the inbox entirely .
• Expect resistance to new systems to come from sunk cost, not from the new tool's quality; the switching cost is felt today, the benefit only later .
• Replace to-do lists with scheduled commitments: deciding "when and where" in advance predicts follow-through better than intention alone .
• Plan for the real cost of time off to be the return, not the trip: wellbeing peaks around day eight and the first morning back is spent sorting urgency, not doing work .
• Recognize that heat degrades prefrontal-cortex-driven decision-making, so treat heatwave workdays as higher-risk for bad judgment calls .