Reasons and Persons

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Reasons and Persons (ISBN 0-19-824908-X) is a philosophical work by Derek Parfit. It focuses on ethics, rationality and personal identity.

It has four parts.

Contents 1 Self-defeating theories 2 Rationality and time 3 Personal identity 4 Future generations

[edit] Self-defeating theories

Part 1 argues that certain ethical theories are self-defeating. One such theory is ethical egoism, which Parfit claims fails due to the Prisoner's dilemma.

Ultimately, Parfit rejects "common sense morality" on similar grounds. Parfit himself does not explicitly endorse a particular view; rather, he shows what the problems of different theories are. His only positive endorsement is of "impersonal ethics" --impersonality being the common denominator of the different parts of the book.

[edit] Rationality and time

Part 2 focuses on the relationship between rationality and time, dealing with questions such as: should we take into account our past desires?, should I do something I will regret later, even if it seems a good idea now?, and so on.

One of Parfit's arguments is as follows: self-interest theorists consider the differences between different persons at the same time is significant in terms of rationality, but do not consider the difference between the same person at the same time to be as significant. But if, as Parfit argues, a non-reductionist theory of personal identity holds, then the difference between different persons at the same time is more like the difference between the same persons at different times. So, if non-reductionism is true, self-interest theorists are inconsistent in viewing spatial relations as significant but temporal relations insignificant (or, vis-a-vis). Thus, the foundations of the self-interest theory are undermined by non-reductionism, which lends support to the present-aim theory of rationality, the critical version of which Parfit favours.

[edit] Personal identity

Part 3 argues for a reductive account of personal identity; rather than accepting the claim that our existence is a deep, significant fact about the world, Parfit's account of personal identity is like this:

At time 1, there is a person. At a later time 2, there is a person. These people seem to be the same person. Indeed, these people share memories and personality traits. But there are no further facts in the world that make them the same person.

Parfit's argument for this position relies on our intuitions regarding thought experiments such as teleportation, the fission and fusion of persons, gradual replacement of the matter in one's brain, gradual alteration of one's psychology, and so on.

Parfit's conclusion is similar to David Hume's view, and also to the view of the self in Buddhism, though it does not restrict itself to a mere reformulation of them. For besides being reductive, Parfit's view is also deflationary: in the end, "what matters" is not personal identity, but rather mental continuity and connectedness.

[edit] Future generations

Part 4 deals with questions of our responsibility towards future generations. It raises questions about whether it can be wrong to create a life, whether environmental destruction violates the rights of future people, and so on.

One question Parfit raises is this: given that the course of history drastically affects what people are actually born (since it affects which potential parents actually meet and have children; and also, a difference in the time of conception will alter the genetic makeup of the child), do future persons have a right to complain about our actions, since they likely wouldn't exist if things had been different?

Another problem Parfit looks at is the mere addition paradox, which supposedly shows that it is better to have a lot of people who are slightly happy, than a few people who are very happy. Parfit calls this view "repugnant", but says he has not yet found a solution.