Cryonics is the practice of preserving people who are dying in liquid nitrogen soon after their heart stops. The idea is that most of your brain's information content is still intact right after you've "died", i.e. medical death or legal death. If humans invent molecular nanotechnology or brain emulation techniques, it may be possible to reconstruct the consciousness of cryopreserved patients.

Related: Life Extension, a more general tag about ways to avoid death.

Cryonics-associated issues commonly raised on LessWrong

Pro-cryonics points

Advanced reductionism/physicalism (because of the issues associated with identifying a person with continuity of brain information).
Whether an extended healthy lifespan is worthwhile (relates to Fun Theory, religious rationalizations for 70-year lifespans, "sour grapes" rationalizations for why death is actually a good thing).
The "shut up and multiply" aspect of spending $300/year (as Eliezer Yudkowsky quotes his costs for Cryonics Institute membership ($125/year) plus term life insurance ($180/year)) for a probability (how large being widely disputed) of obtaining many more years of lifespan. For this reason, cryonics advocates regard it as an extreme case of failure at rationality - a low-hanging fruit by which millions of deaths per year could be prevented at low cost.

Anti-cryonics points

Cognitive biases contributing to emotional prejudice in favor of cryonics (optimistic bias, motivated cognition).
The multiply chained nature of the probabilities involved in cryonics, and whether the final expected utility is worth the cost.
Money spent on cryonics could, arguably, be better spent on efficient charity.
S-risks/hyperexistential risks; The far future may turn out to be dystopian and have negative expected value.

Notable Posts

We Agree: Get Froze by Robin Hanson. "My co-blogger Eliezer and I may disagree on AI fooms, but we agree on something quite contrarian and, we think, huge: More likely than not, most folks who die today didn't have to die! ... It seems far more people read this blog daily than have ever signed up for cryonics. While it is hard to justify most medical procedures using standard health economics calculations, such calculations say that at today's prices cryonics seems a good deal even if you think there's only a 5% chance it'll work."
You Only Live Twice by Eliezer Yudkowsky. "My co-blogger Robin and I may disagre

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