The project of medicine is to save life, yet there is a strong taboo against Promethean medicines which save life to too great a degree. The mythology of human civilisations is filled with precautionary tales regarding the doomed fate of those who seek to postpone or escape death. These taboos are not easily explained; nevertheless the popular sentiment seems to be that, at some point, it would be wrong to extend the duration of a person's life.
Over the past century, the life expectancy of a North American male has almost doubled, mostly through the application of advances in medical technology. This dramatic shift in lifespan has brought about an enormous difference in how we live our lives. We can do more work, have more careers, and have more children who we can expect to outlive us. At the same time, we consume more resources, both in the prime of life, and increasingly in our old age.
Though our lives have already increased in length dramatically, we are approaching a turning-point - there are many medical technologies reaching maturity which will soon offer us the opportunity to increase human lifespan. One day these technologies will extend our lives far beyond what we currently consider a 'natural' lifespan. Whether the gains are modest or dramatic, these therapies will make some difference to the lives of those who receive them.
We are not facing literal immortality, but we will soon develop the technological capacity to significantly increase human lifespan and decrease the symptoms of ageing, violating the widespread taboos. If no ethical decisions are made, many of these technologies will be deployed and our lives will be extended. If there is any rational basis to the taboo against extending life, we need to discover it soon. By the same token, if these technologies will be beneficial, we need to know why.
Both medical research and clinical practice are extremely focused on lifesaving interventions. Current medical practice and current research policy is blind to the effects that medicine has on longevity. This thesis attempts to assess the likely effects that existing and impending medical technologies will have on human longevity, and to assess the normative value of these effects.
I begin with a review of various rationales against the use of medical technologies to extend life, which have been put forward by philosophers, biologists and politicians. Some of these arguments are dismissed here on the basis that they lack merit or that they are unanswerable, and the others are retained for analysis in the subsequent chapters.
Chapter 2 situates the overall analysis within an evidentiary framework, by reviewing the biological processes that underpin ageing and the technologies that have been developed or proposed for combating these processes. In the light of the available evidence, I propose four archetypal health trajectories that an enhanced person's life may follow, depending on the life-extending therapies which are employed. These orthogonal archetypes locate the different extremes that may be produced by different life-extending technologies.
The third chapter seeks to determine the value that each of these archetypes would have for individuals, relative to the value of a normal, un-enhanced life. To do this, I develop a quantified account of utilitarianism based on John Broome's temporal account of benefit and harm. This allows the different health trajectories to be assessed under different assumptions regarding the rate of aged decline and the badness of decrepitude. I then consider various arguments that interfere with the underpinnings of this basic utilitarian account, including several arguments which aim to show that a longer lifespan would be bad for individuals on any theory of value. Following this analysis I am able to sort the archetypal health trajectories by the degree to which they are beneficial or harmful.
As a society, we are concerned mainly with the distributed effects of new medical technologies. Chapter 4 focuses on these collective effects of life-extending medicine. Therapies which are unreasonably expensive, or which produce widespread ill-effects for the population as a whole may be unethical even when they are of benefit to individuals. I assess the likely effects of life extension on basic demographic variables such as population size and composition, and draw some conclusions about the ways in which these effects determine the permissibility of different therapies. I consider the types of sacrifices which will be justified in order to obtain the different kinds of health outcomes that will be produced by the new medical technologies. Finally I address arguments against the use of longevity therapies based on egalitarian principles of justice.
All technologies which aim to enhance the basic functions of human bodies face a precautionary objection, which warns against the unknown dangers of trying to improve on our biological traits which are the products of the process of evolution. Chapter 5 assesses these arguments in the particular case of enhancements which target the biological processes which underpin ageing. I give an explanation of the evolutionary sources of our ageing and mortality, and compare these sources with our needs and goals. An evaluation is made as to whether or fit nature gives us any moral imperative to preserve the status quo.
Finally I am able to draw some broad conclusions about the kinds of limitations which we should place on the development and implementation of medical technologies which extend human lifespan, and whether we should work to live longer than we presently do