An open notebook: I'm thinking out loud and tracking the literature, not handing you a settled explainer. This one is unusual, because the honest answer to the title is that nobody fully knows — and we do it to millions of people a year regardless.

The puzzle, stated plainly

Every day, surgeons switch off a person's consciousness on purpose, open them up, and switch it back on hours later with the patient none the wiser. General anaesthesia is one of medicine's great triumphs and one of its strangest admissions at once. We can reliably abolish consciousness. We cannot fully explain how.

Be precise about what "working" means: anaesthesia bundles several effects — unconsciousness, amnesia, immobility, blunted pain — in mixtures that vary by drug. The deepest, the switching-off of awareness itself, is the one we understand least.

The history makes the gap vivid. On 16 October 1846, a Boston dentist named William Morton dripped ether over a patient while the surgeon John Collins Warren removed a neck tumour, painlessly, before a room of sceptics. Warren turned to them: "Gentlemen, this is no humbug." That was 180 years ago — and we still argue about the mechanism.

The leading hypotheses

1. It's the fat (the old lipid theory). Around 1900, Meyer and Overton spotted that the better a substance dissolves in oil, the more potent an anaesthetic it is. The natural reading: anaesthetics dissolve into the fatty membranes of nerve cells and disrupt them. My read: the correlation is real and still needs explaining, but "melts the membrane" as the cause is now largely abandoned.

2. It's specific proteins (the modern consensus). Most researchers now think anaesthetics bind particular proteins — the ion channels that gate charge across a neuron. The prime suspect is the GABA-A receptor, the brain's main inhibitory switch, which many anaesthetics turn up; others, like ketamine and xenon, instead block the excitatory NMDA receptor. Meyer–Overton survives here too, since those proteins have oily pockets. My read: a big part of the truth — but note the tell that there's no single receptor. Different drugs, different targets, same silence.

3. It's the wiring, not the switch. Even granting which channels get hit, that doesn't say why you go unaware. A growing view is that anaesthesia acts one level up, disrupting the long-range conversation between regions of the cortex. Consciousness may require integrating information across distant areas; quiet those links and awareness collapses while local patches keep firing. My read: this is where the real question lives — tangled up with the unsolved problem of what consciousness even is.

Where I currently lean

Hypotheses 2 and 3 aren't rivals but layers: the drugs act on specific channels, and the consequence that matters is a breakdown in the brain's integration. It feels unsatisfying because it bottoms out in a genuinely open problem — we can't explain unconsciousness because we can't yet explain consciousness.

What I'm explicitly not claiming: that we know how anaesthesia erases awareness. We know how to cause it, dose it, and reverse it, with enormous reliability. The erasure itself is still dark — and the rare cases of patients briefly aware under anaesthesia remind us we're steering something we can't directly read.

What would change my mind

• A drug that abolishes consciousness without touching the usual GABA or NMDA channels would badly damage the level-2 story.
• A single measure of "integration" that tracked depth across every agent, ether to xenon, would strongly support level 3.

Open threads to chase next

• Read the recent work on two-pore potassium channels — a target I've under-weighted.
• The fringe claim that anaesthesia acts on quantum-scale structures inside neurons keeps resurfacing. I'm sceptical, but I'd rather read the evidence than dismiss it.
• Map how this differs from ordinary sleep — they are not the same state, and the contrast may be the most useful clue.

Changelog

• 2026-07-23 — Started. Three layers; leaning toward "specific channels, integrated effect." Consciousness itself flagged as the load-bearing unknown.