In the early 1990s, a neurologist in Iowa began seeing a patient who should have been fine. A tumour had been removed from the front of his brain, and by every standard measure the surgery was a success: intelligence intact, memory intact, language, logic, knowledge, all of it tested normal. The man could analyse a problem as well as he ever had. What he could not do, any longer, was decide. Choosing where to eat lunch became an hour of flawless, endless reasoning about seating and menus and traffic that never arrived anywhere. Scheduling an appointment defeated him. Within a couple of years this previously successful professional had reasoned his way, impeccably, out of a career and a marriage.
What the surgery had damaged was not thinking. It was the circuitry that connects thinking to the body: the channel through which feeling reaches deliberation. The neurologist's conclusion, built over years of similar cases, upended the oldest assumption in Western thought about decisions: that emotion is the enemy of reason, the thing a good decision-maker suppresses. The patients had achieved the philosopher's ideal (pure reason, uncontaminated by feeling) and it turned out pure reason cannot choose. Every option weighs the same. The body's signal is not noise on the line. It is how the mind knows what matters.
Which brings us to a phrase you use more than you'd probably admit in a boardroom: gut feeling.
You have made consequential calls on it. Most founders have, and the good ones quietly trust it more than the deck in front of them. But ask what a gut feeling actually is and the answers go vague: instinct, sixth sense, something mystical that either visits you or doesn't. The Iowa patients say otherwise. A gut feeling is a physical event with a mechanism: your body running a compressed ledger of every comparable situation you have ever lived through, and delivering the balance as sensation (the tightening, the ease, the reluctance in the chest) before conscious analysis has finished loading. It is pattern recognition, rendered somatically, drawing on more data than you can consciously access. When a founder with twenty years of deals feels wrong about a clean-looking term sheet, that is not magic. That is two decades of ledger, reporting.
Now follow the thought to the place nobody follows it, because this is where it stops being interesting and starts being expensive.
If intuition is a signal generated by your body, then the quality of the signal depends on the state of the body generating it. This is true of every instrument ever built and there is no exemption for this one. A depleted system does not stop producing gut feelings. That would almost be safer. It produces corrupted ones. Exhaustion can manufacture dread that reads exactly like a warning about the deal. A nervous system stuck in threat can tag neutral information as danger. Chronic overload does the opposite and flattens the signal entirely, so the pattern that should be screaming reads as nothing at all. The sensation arrives in the same channel, wearing the same uniform, and you have no way of knowing from the inside whether you are receiving twenty years of ledger or four hours of sleep. Your gut on the fourth day of a fundraising trip is not your gut. It is noise with your gut's credentials.
This is why "trust your instincts" is half an instruction, and the dangerous half, on its own. The full version has two clauses the airport books leave out. First: maintain the instrument the instinct runs on, because signal quality is a function of state, and state is manageable. Second: know the conditions under which your readings are reliable, which is knowable, because the accuracy with which people perceive their own internal signals is not fixed or equal. It varies between individuals, it can be assessed, and there is early evidence it can be improved.
Fifteen years of clinical work is, in one sense, an education in exactly this: bodies reporting things their owners haven't registered, and the slow craft of telling a true signal from an artefact. What that work teaches you is that the reading is never just the reading. It is the reading in this system, in this state. The same principle governs the founder's most trusted faculty. Intuition is real. It is also physical, which means it is conditional, and the condition is yours to manage or ignore.
You own an instrument older than language, trained on everything you've ever survived, and consulted at every moment that matters. It has never once been calibrated.