Derek Parfit

Parfit rose to prominence in 1971 with the publication of his first paper, "Personal Identity". His first book, Reasons and Persons (1984), has been described as the most significant work of moral philosophy since the 1800s.^[6][7] His second book, On What Matters (2011), was widely circulated and discussed for many years before its publication.


For his entire academic career, Parfit worked at Oxford University, where he was an Emeritus Senior Research Fellow at All Souls College at the time of his death. He was also a visiting professor of philosophy at Harvard University, New York University, and Rutgers University. He was awarded the 2014 Rolf Schock Prize "for his groundbreaking contributions concerning personal identity, regard for future generations, and analysis of the structure of moral theories."^[8]

The future[edit]

In part four of Reasons and Persons, Parfit discusses possible futures for the world.^{[11]: 349–441} Parfit discusses possible futures and population growth in Chapter 17 of Reasons and Persons. He shows that both average and total utilitarianism result in unwelcome conclusions when applied to population.^[11]: 388


In the section titled "Overpopulation," Parfit distinguishes between average utilitarianism and total utilitarianism. He formulates average utilitarianism in two ways. One is what Parfit calls the "Impersonal Average Principle", which he formulates as "If other things are equal, the best outcome is the one in which people's lives go, on average, best."^[11]: 386 The other is what he calls the "Hedonistic version"; he formulates this as "If other things are equal, the best outcome is the one in which there is the greatest average net sum of happiness, per life lived."^[11]: 386 Parfit then gives two formulations of the total utilitarianism view. The first formulation Parfit calls the "Hedonistic version of the Impersonal Total Principle": "If other things are equal, the best outcome is the one in which there would be the greatest quantity of happiness—the greatest net sum of happiness minus misery."^[11]: 387 He then describes the other formulation, the "non-Hedonistic Impersonal Total Principle": "If other things are equal, the best outcome is the one in which there would be the greatest quantity of whatever makes life worth living.^[11]: 387


Applying total utilitarian standards (absolute total happiness) to possible population growth and welfare leads to what he calls the repugnant conclusion: "For any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better, even though its members have lives that are barely worth living."^[11]: 388 Parfit illustrates this with a simple thought experiment: imagine a choice between two possible futures. In A, 10 billion people would live during the next generation, all with extremely happy lives, lives far happier than anyone's today. In B, there are 20 billion people all living lives that, while slightly less happy than those in A, are still very happy. Under total utility maximisation we should prefer B to A. Therefore, through a regressive process of population increases and happiness decreases (in each pair of cases the happiness decrease is outweighed by the population increase) we are forced to prefer Z, a world of hundreds of billions of people all living lives barely worth living, to A. Even if we do not hold that coming to exist can benefit someone, we still must at least admit that Z is no worse than A. There have been a number of responses to Parfit's utilitarian calculus and his conclusion regarding future lives, including challenges to what life in the A-world would be like and whether life in the Z-world would differ very much from a normal privileged life; that movement from the A-world to the Z-world can be blocked by discontinuity; that rather than accepting the utilitarian premise of maximizing happiness, emphasis should be placed on the converse, minimizing suffering; challenging Parfit's teleological framework by arguing that "better than" is a transitive relation and removing the transitive axiom of the all-things-considered-better-than relation; proposing a minimal threshold of liberties and primary social goods to be distributed; and taking a deontological approach that looks to values and their transmission through time.^[18]


Parfit makes a similar argument against average utilitarian standards. If all we care about is average happiness, we are forced to conclude that an extremely small population, say ten people, over the course of human history is the best outcome if we assume that these ten people (Adam and Eve et al.) had lives happier than we could ever imagine.^[11]: 420 Then consider the case of American immigration. Presumably alien welfare is less than American, but the would-be alien benefits tremendously from leaving his homeland. Assume also that Americans benefit from immigration (at least in small amounts) because they get cheap labour, etc. Under immigration both groups are better off, but if this increase is offset by increase in the population, then average welfare is lower. Thus although everyone is better off, this is not the preferred outcome. Parfit asserts that this is simply absurd.


Parfit then discusses the identity of future generations. In Chapter 16 of Reasons and Persons he posits that one's existence is intimately related to the time and conditions of one's conception.^[11]: 351 He calls this "The Time-Dependence Claim": "If any particular person had not been conceived when he was in fact conceived, it is in fact true that he would never have existed".^[11]: 351


Study of weather patterns and other physical phenomena in the 20th century has shown that very minor changes in conditions at time T have drastic effects at all times after T. Compare this to the romantic involvement of future childbearing partners. Any actions taken today, at time T, will affect who exists after only a few generations. For instance, a significant change in global environmental policy would shift the conditions of the conception process so much that after 300 years none of the same people that would have been born are in fact born. Different couples meet each other and conceive at different times, and so different people come into existence. This is known as the 'non-identity problem'.


We could thus craft disastrous policies that would be worse for nobody, because none of the same people would exist under the different policies. If we consider the moral ramifications of potential policies in person-affecting terms, we will have no reason to prefer a sound policy over an unsound one provided that its effects are not felt for a few generations. This is the non-identity problem in its purest form: the identity of future generations is causally dependent, in a very sensitive way, on the actions of the present generations.