In a recent post at Depressed Metabolism Aschwin de Wolf discusses arguments against cryonics - the low temperature storage of the deceased that aims to preserve the data contained in the brain. For example, what would be needed to make a rational, scientific case against cryonics?
What is striking about cryonics is that those who have taken serious efforts to understand the arguments in favor of its technical feasibility generally endorse the idea. Those who have not made cryonics arrangements usually give non-technical arguments (anxiety about the future, loss of family and friends, etc), lack funding or life insurance, or are (self-identified) procrastinators. In contrast, those who reject cryonics are almost invariably uninformed. They do not understand what happens to cells when they freeze, they are not aware of vitrification (solidification without ice formation), they think that brain cells "disappear" five minutes after cardiac arrest, they demand proof of suspended animation as a condition for endorsing cryonics, etc.
his does not mean that no serious arguments could be presented. [For example, it could be argued that] memory and identity are encoded in such a fragile and delicate manner that cerebral ischemia, ice formation or cryoprotectant toxicity irreversibly destroy it. Considering our limited understanding of the nature of consciousness, and the biochemical and molecular basis of memory, this cannot be ruled out.
Cryonics advocates can respond to such a challenge by producing an argument that pairs our current understanding of the neuroanatomical basis of identity and memory to a cryobiological argument in order to argue that existing cryonics procedures are expected to preserve it. An excellent, knowledgeable, response of this kind is offered in Mike Darwin's Does Personal Identity Survive Cryopreservation? Cryonics skeptics in turn could produce evidence that existing cryonics procedures fall short of this goal.
To my eyes, the weight of evidence presently favors low temperature vitrification being an adequate methodology to preserve the data of the brain. The practice could be greatly improved upon in many ways, such as by eliminating the toxicity of chemicals that must presently be used. There is always room for revolutionary improvement in any technology, but vitrification as it stands seems to be up to the bare essentials of the job: preserve the data sufficiently well for later restoration of a human mind.
Sadly most of the arguments made against cryonics are far from scientific and rational, and in this it is in a similar position to research into the biotechnologies of engineered human longevity. Most people argue against radical life extension from the gut, not the head, when they are first introduced to the concept. It is an instinctive rejection of anything that looks like change: one of the less helpful aspects of human nature at work. People are fiercely defensive of the norm, whatever the norm might happen to be, even when it involves ongoing preventable deaths on a massive, staggering scale.
The human death toll in the Year 2001 from all 227 nations on Earth was nearly 55 million people, of which about 52 million were not directly caused by human action, that is, not accidents, or suicides, or war. They were "natural" deaths.