Medicine

The core idea in plain words

Medicine is the science and craft of keeping a body working, and repairing it when it breaks. It sits on top of biology, the way engineering sits on top of physics: biology tells you how cells, tissues and organs work; medicine asks what to do when they don’t.

Every medical act, from a doctor’s question to brain surgery, comes down to three steps:

Diagnosis — what is wrong?
Prognosis — what will happen if we do nothing?
Treatment — what can we do to change that, and at what cost?

The rest is detail — a vast, fascinating, life-saving amount of detail.

An analogy: the mechanic and the city

A car mechanic deals with a machine that was designed, has a manual, and holds still while you work on it. A doctor deals with something more like a city: millions of semi-independent workers (cells), supply lines (blood vessels), a communications network (nerves and hormones), a police force (the immune system), and waste disposal (kidneys and liver). Nobody wrote the manual. The city never shuts down for repairs. And intervening in one district often causes trouble in another — that is what we call a side effect.

This is why medicine is humble about its knowledge in a way physics need not be. It works by careful observation, by controlled trials, and by always asking “compared to what?”.

The main branches

Anatomy — the structure: what is where.
Physiology — the function: how it works when healthy.
Pathology — what goes wrong, down to the cells.
Pharmacology — how drugs act on the body, and how the body acts on drugs.
Epidemiology — patterns of disease across whole populations; how we know smoking causes cancer.
Clinical specialties — cardiology (heart), neurology (nerves), oncology (cancer), and dozens more.
Psychology and psychiatry — the mind, which is never separate from the body.

A worked example: what a test result really means

You take a screening test for a disease. The test is “99% accurate”: it catches 99% of people who have the disease (sensitivity) and correctly clears 99% of people who don’t (specificity). It comes back positive. How worried should you be?

It depends on how common the disease is. Say 1 in 1,000 people have it. Test 100,000 people:

100 have the disease; the test catches 99 of them.
99,900 don’t; 1% of them, about 999, test positive anyway.

So there are 99 + 999 = 1,098 positives, and only 99 are real. The chance you are actually ill is

\frac{99}{1098} \approx 9\%.

Not 99% — nine. This is Bayes’ theorem doing quiet, life-changing work, and it is why doctors confirm a positive screening result with a second, different test before acting. It is also why “test everyone for everything” is not as clever as it sounds: with rare conditions you generate mostly false alarms, and false alarms lead to anxiety, more tests and sometimes harmful treatment.

How we know a treatment works

The gold standard is the randomised controlled trial: take a group of patients, randomly split them, give one half the treatment and the other a placebo or the current best treatment, and — ideally — keep both patients and doctors blind to who got what. Randomisation stops us fooling ourselves by giving the drug to the healthier patients; blinding stops expectation from colouring the results.

Above single trials sit systematic reviews and meta-analyses, which pool every good trial on a question. Below them sit observational studies, case reports and, at the bottom, “it worked for my cousin”.

Common misconceptions

“Natural means safe.” Hemlock is natural. Digoxin, a heart drug, comes from the foxglove. The dose and the evidence matter, not the origin.
“Antibiotics cure colds.” Colds are viral; antibiotics only kill bacteria. Taking them needlessly breeds resistant bacteria.
“If I feel better, the treatment worked.” Most illnesses get better on their own (regression to the mean), and the placebo effect is real. That is precisely why we need control groups.
“Doctors know everything about the body.” Medicine is still young. We understood germs only in the 1860s–80s; we are still learning about the gut microbiome, the immune system and the brain.

Health is more than medicine

Most of what keeps you well happens outside the clinic: sleep, movement, food, friends, and not smoking. I’ve written about that side — breathing, stretching, fasting — on the Health page and in the essays on breathwork.

Connections

Biology — the science underneath.
Anatomy — the map of the body.
Psychology — the mind side of health.
Health — practical notes on diet, stretching and fasting.
Physics — from X-rays to MRI, much of modern diagnosis is applied physics.