Reasons and Persons

Derek Parfit

Book cover

This is an extraordinary book. It is also challenging and also imperfect. I don’t agree with everything Parfit has to say, but R&P has done as much as any book to make me think hard about philosophical issues. (As a side note, I got interested in reading this book from watching Shelly Kagan’s Yale course on Death–highly recommended as a more digestible introduction to some similar topics–as well as, unfortunately, from reading about Parfit after his recent death.)

It’s difficult to know where to start, without just writing an extremely long (even by my standards!) recap of the book. For me, the most engaging part of the book is the middle section, on personal identity. (This is the part closely related to the Kagan course.) Parfit argues for a reductionist view of the self (no appealing to immaterial “souls” that we don’t have any clear evidence to support), and follows this argument through to some counterintuitive and perhaps unsettling conclusions. He works through a number of thought experiments regarding teleportation, brain transplants, and other fanciful scenarios, to develop the conclusions: briefly, that personal identity merely consists of psychological connectedness in terms of memories, intentions, and so forth, and that there is “no further fact” regarding personal identity that we can appeal to. So when you step into the Star Trek transporter, and ask whether you are about to wake up on the planet’s surface or whether you’re about to die, there is no answer to this question. Although his arguments are based on fairly fantastical thought experiments, I find them pretty convincingly argued. Parfit’s view on identity has a very wide range of implications, in terms of both ethical theory and the way we ought to live our lives (and, by extension, the way we ought to think about our deaths). I am far from done thinking about these things. But one main conclusion that Parfit draws out in the book is that the relationship between our current, past, and future selves is more similar than we intuitively feel to the relationship between our current selves and other selves. He draws out this idea in a concrete argument in favor of rules preventing people from behaviors that are too harmful to their future selves. More generally, Parfit’s view favors “impersonal” ethical perspectives that are not excessively focused on “the self through time” as a unit of analysis.

The remainder of the book is also interesting, though it was a bit more slow-going for me. His discussion of ethical theories is extensive, yet (refreshingly?) inconclusive. He demonstrates weaknesses in several ethical theories but does not have a ready answer to what might constitute a totally consistent and worthy theory. The last part of the book is an extended discussion of population ethics centering around the “repugnant conclusion” (so dubbed by Parfit)–that based on a set of seemingly unobjectionable premises for a consequentialist ethics, it is difficult to avoid the conclusion that it is better to have a universe of trillions of people with lives barely worth living, than the current universe or indeed any universe with a smaller number of happier people. This is a fascinating thought experiment, and again, while I don’t have any clear response to it, it is very thought-provoking.

My first observation is that Parfit seems oddly inconsistent in his willingness to question his intuitions. In the personal identity section, he is willing to accept the “no further fact” conclusion, though he admits he finds it difficult to grasp intuitively, simply because it so clearly follows from premises that he sees as unassailable. Yet he is extremely unwilling to accept the repugnant conclusion, even though the situation is quite parallel. I wonder what accounts for this difference.

I feel compelled to draw the conclusion that the existence of the repugnant conclusion stands as something of a rebuke to humans who would “play god.” It may be that it fundamentally makes no sense to argue that hypothetical and totally unconnected universes can be compared to conclude which one is better. (This would be somewhat analogous to the no-answer conclusion on the transporter.) Why should we expect such conclusions to be possible, or indeed, even desirable? The questions are seemingly similar to high-level policy questions regarding, e.g., climate change, which Parfit uses as an example (more or less). But in reality those questions always involve either (a) differential impacts on actually-existing people, or (b) extreme uncertainty around outcomes (or both). Parfit works with examples containing certain outcomes (there will be X number of human lives with Y total utility each), under the presumption that this is a simplifying assumption that brings the key questions into sharper focus. But I’m not sure this is the case. In decisions with world-level consequences, (Knightian) uncertainty seems to be a fundamental and very important aspect, and I’m not sure that conclusions drawn under certainty continue to hold. (Again, we’re not gods.)

I think the book also contains some unintentional clues to problems with the repugnant conclusion. Near the very end, Parfit has a discussion of a hypothetical example of generational decision-making, involving some sort of dying-earth scenario (it’s been a while since I finished and I don’t have the book at hand). The scenario is meant to be a concrete instantiation of the repugnant conclusion. But what interested me was that with the concrete frame, the “repugnant” conclusion came to seem a lot more intuitive and believable. (In part, I think this was because of our natural intuition of uncertainty in concrete cases–there seems to be value in an unending series of barely-worthwhile lives, in part because we have a sense that something good might happen!)

Finally, it might be that, to a god with a “view from eternity” of the world, the repugnant conclusion would be eminently sensible, but also that it does not extend to humans, with our limited perspectives and enormous uncertainty. Religious and mythological writing is filled with the idea that gods might have ideas of justice that are completely unintelligible to us.

My Goodreads rating: 4 stars