These days, it seems like the reasonable promise of biotechnology has become INDEFINITE LONGEVITY.   Actually, that goal was first articulated by the French enlightenment thinker Condorcet.  In order for our pursuit of happiness to be turned into real happiness and for our longings to be undistorted by the prospect of death, the duration of particular human lives have to become long enough and indefinite enough that literally we will not be able to count the days.

 That goal, Condorcet was clear, would be achieved by medical science, although he was necessarily pretty vague about how.  His somewhat reasonable faith was in the indefinite progress of science.

Condorcet knew, of course, that human beings longed for immortality.  And he was just about as certain that there was no God to free us from our biological limitations.  But he also was pretty certain that most of those limitations could eventually be overcome by us, by free beings with the ability to change nature with themselves in mind.  Now he didn't think they could be completely overcome.  He never doubted that each of us would die eventually.  But death, his scientific hope was, would need not come for any particular human being at any particular time.  So it would never seem necessary to any of us.  The necessity of death, which for now is so important in determining who we are, would be turned into an accident.

 We can be a lot less vague about what Condorcet had in mind.  Those transhumanists who talk about immortality, about human beings somehow becoming completely other than biological beings, don't make much sense.  It's the body that animates the mind, and pure, disembodied consciousness—something like Aristotle's God—couldn't act, couldn't be aroused.  Even if our bodies became something other than flesh and blood, even if they became wholly artificial or manmade, they would still be bodies, and so subject to accidental and eventual destruction. 

 So the only way we could become immortal is to bring the whole cosmos under our personal control.  Actually, the only I could achieve immortality through my own efforts is to bring the whole cosmos under MY personal control.  As long as I don't control YOU, after all, you remain a threat to me.  I could only become immortal if I'm free and rational enough to make myself into the God described in the Bible. And even the Biblical Creator didn't MAKE himself who he is.

 Living as we do at the dawning of the biotechnology of regenerative medicine, here's what really seems possible: Maybe every part of the body—including, of course, the heart and the kidneys—could be regenerated or replaced.  And perhaps the brain itself—although irreplaceable—could be kept from degenerating.  Then an older person would become like a classic car.  If well maintained (and with the ready availability of spare parts), he could go chugging along for who knows how long?  Nobody could say that he would necessarily stop working at this or that age, especially if he was extremely prudent in attending to the risk factors—the accidental forces—that could stop his motor, extinguish his being.  Regenerative medicine—aided by nanotechnology and all that (it goes without saying I don't understand the details)--provides the promise that we can overcome the necessity of bodily decay.

 Will indefinite longevity be the secret to human happiness?  Well, there's no denying that people would rather not die at any particular time, and that there's a lot of misery in being governed by the scarcity of time.  Time, we can't help but notice, ruins or undermines at least most forms of human enjoyment.  That's why, we can say, that human beings have always longed for immortality, to be freed from the miserable constraints of their self-conscious mortality.  When thinking about immortality, we can't help but begin with the Greek gods—who were self-conscious but didn't die.  They were, in other words, in many respects like our vampires.

 But the immortality of the  Greeks gods was even meant to make sense or be a realistic possibility.  The poets invented them—like today's poets employ the Vampires--to show that immortality isn't only impossible but undesirable.  And so if we thought about who we are, we'd actually chose the mortality with which each of us stuck anyway.  Our longing for immortality is best satisfied by accomplishments that stand the test of time—the immortal glory of the great political deeds or of the enduring beauty and wisdom of works of art or literature--although even our fame, we really know, doesn't last forever.  And we can achieve a kind of immortality through our minds, through knowing the eternal truth about natural necessity, through philosophy.  Everything great that we do—from having children to writing THE REPUBLIC –depends on being mortal.  The polymorphous human eros that animates us, in other words, depends upon death. Only mortals know what it means really to fall in love.

But the Greeks still didn't quite know what to do with the fact that, after all the realistic therapy of the poets and philosophers, we still really didn't want to die.  The Greeks couldn't quite deny the wisdom of Woody Allen, who said he didn't want to achieve immortality through his work, he wanted to achieve it through not dying.  A more vulgar way of expressing the same thought, of course, is:  I don't want to live on through my children, I want to live on by not dying. 

Living the trivial, unerotic, and weightless life of a Greek God, someone might say (our transhumanists do say!), is better than being dead.  Homer  could come up with a character who would chose mortality out of love— like the occasional vampire does—but he still leaves us wondering both  how many of us would have the wisdom to make that choice and whether, all factors considered, the choice was even reasonable.  Avoiding death or embracing love!  It seems like a choice way above the human paygrade.  The vampires, we notice, aren't doing that well with it.

That's why the Greeks had to emphasize that that choice is not given to us.  Philosophy is learning how to die, how to live as well as possible in light of the invincible truth of one's own mortality.  But even Socrates would rather not die at any particular time, and his courageous confrontation with the Athenians at age 70 depended, in part, upon his knowledge that, no matter what he did, he didn't have much time left anyway.  Philosophy may depend upon being mortal, but dead men don't philosophize.