Cryonics Wikipedia has an article about

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". If humans invent molecular nanotechnology or brain emulation techniques, it may be possible to reconstruct the consciousness of cryopreserved patients.

Cryonics-associated issues commonly raised on Less Wrong

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.

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