Profile image
By ScienceBlogs (Reporter)
Contributor profile | More stories
Story Views

Last Hour:
Last 24 Hours:

Derek Parfit, Ex-Philosopher [Stoat]

Saturday, January 7, 2017 12:09
% of readers think this story is Fact. Add your two cents.

Or, “philosophy advances one funeral at a time“? Oddly, no-one has ever said that ( – no, I’m right: no-one ever has) because of course it doesn’t fit. Philosophy isn’t like science, with clear progress that rather leaves the Emeritus behind it. DP says otherwise in his magnum opus, OWM, but doesn’t prove the point.

So: news reaches me of the death of Derek Parfit, Philosopher. I am entirely unaware with his work, although the name is very vaguely familiar. Some people I respect pointed me initially at The whole philosophy community is mourning Derek Parfit. Here’s why he mattered (Vox). I read it and am unimpressed. I am then pointed to HOW TO BE GOOD: An Oxford philosopher thinks he can distill all morality into a formula. Is he right? (NY). Again, I am unimpressed. Today, finding myself surfeited of sci-fi in Waterstones, I browse his “On What Matters”, volume 1. After reading the preface, and then more-and-more rapidly skipping, I got to page 200 without finding anything of interest and stopped.

This post is to record some notes of my reactions. As you’ll see from the above, they hardly amount to a careful review by someone thoroughly familiar with his work, so if that’s what you want, go else where. They are mostly a record for myself, in case I ever wish to revisit (so why on this blog, rather than my personal one? Because the post got too long).


Section: “Why personal identity doesn’t matter”. I suppose I should warn you (if you need warning; you shouldn’t) that I’m reacting to what I read. Whether “Vox” have faithfully paraphrased his work I cannot tell; although some is directly his words. A thought experiment: we take a person (Parfit) and split his brain into two halves, implanting them in two brainless bodies we happen to have handy, and since this is a thought experiment we waive any medical implausibilities. Then “Each of the resulting people believes that he is me, seems to remember living my life, has my character, and is in every other way psychologically continuous with me,” And then proceeds to draw conclusions (of the ordinary semi-paradoxical and totally familiar from various sci-fi novels sort) from this thought experiment. However, the conclusions are only valid if the experiment is actually possible. If it isn’t1, all of the conclusions are null. So I am unable to understand why his conclusion – identity doesn’t matter – is supposed to hold in the real world.

There then follows another thought experiment (the A / A+ / B- / B one, read the link if you care about the details) which is essentially a shell game: it works only because, if you’re not careful, you fail to notice that he changes the definition of “better” (which he is careful never to write down explicitly) when making different comparisons. And all of this to get to nothing more interesting than “Z is a world with vastly, vastly more people — 100 billion, or 200 billion, say — all living lives that are just barely worth living. Parfit’s reasoning suggests that this is better than a much smaller world where people are, on average, much happier. This ludicrous-sounding suggestion…” But why is this suggestion ludicrous? It might be, if you’re a nice comfortable philosopher facing the horror of imagining just about scraping by. But if you imaging yourself as a randomly selected one of the 100 or 200 billion, facing a 93-in-100 or 193-in-200 chance of being rubbed out in the transition to a present-day-Earth-population world, it is very easy to see that you might prefer the over-populated world. So again, I fail to understand: Parfit appears to do nothing more than state a commonplace, badly, and with invalid reasoning.

Then there’s a bit about Altruism. Altruism is good, I agree. But Some of us ask how much of our wealth we rich people ought to give to these poorest people. But that question wrongly assumes that our wealth is ours to give. This wealth is legally ours. But these poorest people have much stronger moral claims to some of this wealth. We ought to transfer to these people, in ways that I mention in a note, at least ten per cent of what we earn is to my mind poorly reasoned (see OWM, below, which seemed much the same). There is more blurring of words; “ours” needs a consistent meaning if his sentences aren’t to turn into mush. He introduces 10% with no apparent justification at all. He might, perhaps, justify it from experience: the church used to claim a much-hated 10% tithe and perhaps 10% is an empirically-sanctioned balance between non-trivial and not-too-onerous.


The NY piece is, bizarrely, illustrated by DP costumed as a coal miner (or perhaps a thought experiment blew up in his face?). We start with the same two-brain thought-experiment of Vox, then we get Parfit is thought by many to be the most original moral philosopher in the English-speaking world which seems weird to me. I’d pick Hayek over DP any day.

It then continues with Suppose that a scientist were to begin replacing your cells, one by one, with those of Greta Garbo at the age of thirty. At the beginning of the experiment, the recipient of the cells would clearly be you, and at the end it would clearly be Garbo, but what about in the middle? It seems implausible to suggest that you could draw a line between the two—that any single cell could make all the difference between you and not-you. How dull. This isn’t even new; it’s a version of the paradox of the heap or the ship of Theseus, but with the bonus of not actually being possible.

On What Matters

Like I say, I browsed it. The preface was a rather dull attempt to introduce his pet philosopher, Henry Sidgwick. The text… just didn’t stick in my mind, so I can tell you nothing useful about it at all. It seemed, ironically for a book entitled “On What Matters”, not to matter at all.

From the NY piece I read After Parfit finished “Reasons and Persons,” he became increasingly disturbed by how many people believed that there was no such thing as objective moral truth. This led him to write his second book, “On What Matters,” and now I read that, I do recall various places where he did, effectively / implicitly (but I do not recall explicitly) assert the existence of objective morality. This is a familiar philosophical problem, because neither pure objectivism nor pure relativism seem plausible, but I cannot recall anything he wrote that made the issue any clearer.

NY says Parfit believes that there are true answers to moral questions, just as there are to mathematical ones2. Humans can perceive these truths, through a combination of intuition and critical reasoning, but they remain true whether humans perceive them or not and this seems to be much the same as Hobbes’s precept or law of nature:

A ‘law of Nature,’ lex naturalis, is a precept or general rule found out by reason by which a man is forbidden to do that which is destructive of his life or taketh away the means of preserving the same, and to omit that by which he thinketh it may be best preserved. For, though they that speak of this subject use to confound jus and lex, ‘right’ and ‘law,’ yet they ought to be distinguished; because ‘right’ consisteth in liberty to do or to forbear, whereas ‘law’ determineth and bindeth to one of them; so that law and right differ as much as obligation and liberty; which in one and the same matter are inconsistent… consequently it is a precept or general rule of reason ‘that every man ought to endeavour peace as far as he has hope of obtaining it, and, when he cannot obtain it, that he may seek and use all helps and advantages of war.’ The first branch of which rule containeth the first and fundamental law of Nature, which is, ‘to seek peace, and follow it.’ The second, the sum of the right of Nature, which is, ‘by all means we can, to defend ourselves.’

I far prefer Hobbes’s language to DP’s.


1. FWIW, I’d go for “it isn’t”, though I’d admit that I can’t demonstrate it. Our current world doesn’t have the surgical ability to split a brain in half, transfer it to two other bodies, and have them live. Quite possibly a future world might. But I think that were it done, the two would be recognisably not two copies of the original. Also (FWIW, and since it came up on fb) I think QM effectively prohibits “copying” brains, to the level of detail that would be required to duplicate people.

2. A slippery arguement to make, when faced with things like the axiom of choice.


We encourage you to Share our Reports, Analyses, Breaking News and Videos. Simply Click your Favorite Social Media Button and Share.

Report abuse


Your Comments
Question   Razz  Sad   Evil  Exclaim  Smile  Redface  Biggrin  Surprised  Eek   Confused   Cool  LOL   Mad   Twisted  Rolleyes   Wink  Idea  Arrow  Neutral  Cry   Mr. Green

Top Stories
Recent Stories



Top Global


Top Alternative




Email this story
Email this story

If you really want to ban this commenter, please write down the reason:

If you really want to disable all recommended stories, click on OK button. After that, you will be redirect to your options page.