Like most of us, Benjamin Franklin did not want to die. Late in his life he expressed the wish that some method of preserving corpses might be found which would allow them eventually to be resuscitated. "Having a very ardent desire to see and observe the state of America a hundred years hence," he wrote in 1773, "I should prefer to an ordinary death, being immersed with a few friends in a cask of Madeira, then to be recalled to life by the solar warmth of my dear country!"
Franklin may be dead but his dream of immortality isn't. Right now, at life extension foundations around the US, there are dozens of corpses submerged in vats-not of Madeira, but of liquid nitrogen. The hope is that scientific advances will permit the deceased to be resurrected, not in time for the millennium but perhaps by the start of the 22nd century.
One of these cadavers, according to legend, is that of Walt Disney. He is said to have elected to have his entire body deep-frozen-a needlessly extravagant choice. As anyone will tell you, the real vehicle of personal identity is not the body but a mere three-pound component of it: the brain. Hundreds of others have made arrangements to have their heads cut off with chain saws immediately upon being declared dead, and put in cryogenic suspension in earthquake-proof "cephalaria."
Is all this just a waste of liquid nitrogen? True, freezing bodily tissue damages each and every cell. But such damage could be repaired by an army of molecule-sized robots-just the sort of thing we'll be seeing in the next century, thanks to the emerging field of nanotechnology (from nanos, Greek for "dwarf"). As for what to do with the thawed-out brains, that's the easy part: lodge them in a fresh body cloned from a bit of the deceased's DNA. The newly resurrected person will notice a sharp experiential discontinuity but will be oblivious of the decades-long "biostatic coma" which has finally ended.
Should this resuscitation scheme be realised in the next century-and, given that each part of it is technologically plausible, who's to say it won't-immortality will still not be assured. One problem is that brain cells, like all the other non-reproductive cells in the body, are programmed to self-destruct within a finite time. Freezing such cells delays the onset of their suicide but does not eliminate it.
But let's suppose, again plausibly, that a way is found to disable the suicide programme encoded in the brain cells' DNA. Although the cells would still wear down, over time, this entropy could be corrected by mini-robots. Then the brain would be immortal. Yet it is still subject to the risk of being destroyed in an accident-a probability which, given sufficient time, approaches 100 per cent. Once the brain is vaporised, any hope for the persistence of personal identity would vanish.
Unless, that is, there was a back-up copy. Not even the giddiest futurist is proposing that we shall be able soon to build a perfect working replica of a given person's brain. But this might not be necessary. The important thing about the brain is not the lump of spongy grey meat, but the stream of mental life it supports. The psychological continuity that gives rise to personal identity is a matter of brain activities involving memory, belief, desire-all of which, in theory, could be downloaded into a computer. Once this software of personal identity is extracted from the brain, the possibilities are endless.
The only real remaining threat to immortality is the end of the universe-either through eternal expansion or in the Big Crunch. Believers in eternal life have both scenarios covered. For the former, the physicist Freeman Dyson has imagined implanting our minds in interstellar dust clouds. For the latter, Frank Tipler argued in The Physics of Immortality that the energy of the Big Crunch could be harnessed to provide infinite computational power in the last second.
If such prospects for eternal life seem rather tedious, there are still the old ways of achieving immortality: through our children or our work. Those weren't enough for Ben Franklin or Disney-or, for that matter, Woody Allen, who once sensibly said: "I don't want to achieve immortality through my work. I want to achieve immortality through not dying."
