Mere addition paradox

The mere addition paradox is a problem in ethics, due to Derek Parfit, and first appearing in his book, Reasons and Persons. The problem leads to what Parfit calls the repugnant conclusion.

The paradox

The paradox appears to show that it is better to have a large population, where everyone has a life that is just barely worth living, than a small population where everyone is very happy.

The paradox arises from consideration of three different possibilities. The following diagrams show different populations, with population size on the x-axis, and the happiness of each individual on the y-axis. Note that for each group of people represented, everyone in the group has exactly the same level of happiness.

In population A, everyone is very happy.

Population A Plus consists of 2 groups - the same group as in A has had added to it a group who are less happy, but whose lives are nevertheless worth living. As this is a mere addition of people with lives worth living, Parfit argues that it is no worse than the state of affairs in A.

Population B is the same size as population A Plus, but the average happiness is higher than A Plus, though slightly lower than in A. Since the average happiness is higher than in A Plus, Parfit argues that the state of affairs in B is no worse than that of A Plus, and therefore, no worse than that of A.

The paradox comes because this argument is repeatable until we reach something like Z, a huge population of people whose lives are only just worth living (on these graphs, negative values would indicate lives not worth living).

Thus, the state of affairs in Z is no worse than the state of affairs in A. Parfit calls this the repugnant conclusion, and rejects it, but says he does not have a solution.

Objections and resolutions of the paradox

Some say that this paradox can be defeated by simply denying its first assumption: that adding people of less-than-average happiness into the world doesn't make the overall situation worse. This is by no means universally accepted, and there is a branch of utilitarianism that aims at maximising the average happiness. However, this position does involve the claim that it is actually bad for people of less-than-average happiness to be born, even if their lives are worth living.

Alternatively, one could deny that the redistribution of happiness in the move from A Plus to B makes things better. One could claim instead that A Plus is better than B. However, this would seem to involve the claim that what is most important is the happiness of the happiest people, and a small increase in that is worth a (bigger) decrease in the happiness of less happy people.

One might say that, actually, the addition of people with a very low level of happiness can be bad in itself, even if their lives are worth living. This implies a threshold of happiness below which it is bad for someone to be born, even though life would be worth living. Parfit calls this threshold "the bad level", but argues that it is likely to be too low to effectively prevent the repugnant conclusion, applying only to lives that are "gravely deficient" and which, "though worth living ... must be crimped and mean."

The latter can be resolved by stating that for this person it is not bad be born at all, but bad to be born at the given time, simultaneously with many other persons in the same situation. If more and more people live at the same time at a given place, life gets miserable for all.

The paradox is also weak in one of its assumptions: Adding people of much less-than-average happiness into the world makes life more miserable for the formerly happy people (group A) as well, because they are confronted with poverty and diseases in people they know, possibly friends or even loved ones -- One might be inclined to help only the friends, but this will make them dependent on you and this dependency usually destroys a friendship after a while and reduces it to a mere façade.

The knowledge and sight of outrageous injustice is quite incompatible with true happiness for most people on both sides, see also the results about the "Tit for Tat" strategy on iterated prisoner's dilemma. One might argue that the groups could be isolated from each other and the rich ones could just ignore the others. But this means that society falls apart and that life is based on ignorance and lies. Knowing and facing the truth about reality constitutes an important part of happiness, particularly but not exclusively for scientists and artists.

In addition, the formerly happy people may contract diseases from the miserable ones. They might also live in fear of a revolution, so they need weapons, again isolation and protection against them, making life miserable for themselves, too.

Human history is a source of many examples of the points mentioned above.

The reasoning is similar to the discussion about the reintroduction of torture: On a very hypothetical basis and remote of the real experiences history taught us, abstract subtleties are discussed in order to question established principles of civilization.

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Mere+addition+paradox Wikipedia article Mere addition paradox.