What donating a kidney has to do with critical thinking

Anonymous | November 19, 2024

Who knew critical thinking applied to everyday life? I’ve always thought critical thinking was too hard (and too dry — sorry to those who tried to convert me). I felt it was something only for brainy people. Then one day I realised I had used it when I was thinking of donating my kidney.

What I knew about kidney disease

Kidney disease isn’t much fun. People feel sick and tired, and are just not themselves. At some point, they could need dialysis, often three times a week, for about half a day each time. That’s like having a part-time job. (Other types of dialysis exist, but may not be suitable.)

By the time someone needs dialysis, they’ll need it regularly. They can’t skip a session because they want to do something else. Holidays and trips away need to be carefully planned. Despite dialysis, the person’s health deteriorates, and life expectancy is limited.

How I used deductive reasoning when I decided

I thought, I have two kidneys, but I only need one. Why don’t I give my ‘spare part’ to someone who needs it more? That was me applying deductive reasoning without realising it.

Deductive reasoning starts with two or more truths, then draws a logical conclusion from them. If X and Y are true, Z must be true.

X: People with two healthy kidneys can give one away.

Y: I had two healthy kidneys.

Z: Therefore I could give one away.

Months of rigorous tests and scans confirmed that yes, I had two healthy kidneys. Fantastic!

How I used inductive reasoning when I considered the risks

Giving away a kidney is safe, but not completely risk-free, so I had to think about the different risks. Here’s how I approached one of them.

Again without realising it, I applied critical thinking. This time, it was inductive reasoning: starting with two or more observations, then coming to a likely conclusion. If X and Y are true, Z is probably true, but not guaranteed.

X: I donate my kidney.

Y: Kidney donors have a slightly higher chance of kidney disease than non-donors, but the chance is still low.

Z: Therefore I might develop kidney disease, but I probably won’t.

Only 3 out of 1,000 kidney donors develop kidney disease. That means 997 in 1,000 donors do not. (In contrast, 2 out of 1,000 non-donors develop it. For reference, 50 out of 1,000 people develop bowel cancer.)

I’ll do everything I reasonably can to minimise my risks. I’ll keep exercising, maintain a healthy weight, and eat a healthy diet with plenty of fruit and vegetables. And if I still develop the disease, so be it. I might have developed it anyway — who knows?

So far, so good

Some time on from the surgery, I’m feeling completely myself. Nothing’s changed, except I have a few faint scars. And of course, my ex-kidney is in someone else’s body — I wonder if that counts as an out-of-body experience?

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(Last updated: February 2025)