In an uninteresting sense, all traits have both a "nature" and "nurture" component.

These categories would be better named as genetic/biological and environment/ideas. (I'll use mixed terminology, the important thing is to bear in mind what it means.)

Without genes, you won't get a person. Genes create the brain. If genes were different, you'd get a body without a brain or lungs, or nothing larger than an egg. And different genes, in the right situation, make a flower or a tree instead of a person.

Without environment, you'd never get a person either. You think eye color is purely genetic? Not if the fetus doesn't get enough nutrition from its environment. It will die without having eyes, without an appropriate environment to help it.

So, trivially, all traits have nature and nurture involved.

Now let's consider a liberal. Why is he a liberal? How can we explain it? It's a matter of ideas. There is nothing in his genes about liberalism.

Liberals are liberals because they have *knowledge* about liberalism. What is the origin of that knowledge? It's from our culture and its political traditions, from books, from thinking, from discussions, from the TV, and so on. Liberalism isn't a part of our genes, even though, yes, our genes are necessary for creating the brain which is needed to understand liberalism.

There's always an idea-based explanation of why a person is a liberal, which explains where the knowledge came from. His parents told him, or he figured it out himself, or he read it in _Liberalism_ by Ludwig von Mises, etc, he did not find liberal arguments in his genes.

Note that "knowledge" is not "justified, true belief". There is no assumption that knowledge isn't mistaken or that the holder understands its nature. Anti-liberals have knowledge too, even though liberals and anti-liberals can't both have the truth of the matter.

The nature/nurture debate -- the heart of it, I think -- revolves around questions like:

1) Where does the knowledge that determines if a person is liberal/happy/smart/gay/light-hearted/extroverted/many-other-things come from?

2) If a person wants to change, what interventions will be effective?

The "conventional/standard" view among *lay* people and the news media gives the following answers:

1) Around 20% of the knowledge for high level personality traits and other uniquely human features (things not found in animals) is from genes, and 80% from upbringing/etc.

2) If the knowledge is from upbringing, then it can be changed by learning new ideas, but if it's from genes then it's permanent/unchangeable.

BTW this view has sometimes been claimed to be a consensus of scientists, but it's not. For example, the expert geneticist Sahotra Sarkar not only disagrees but reports that most competent geneticists know that the heritability approach has been criticized in the literature and use other, better methods instead. The heritability approach these conclusions largely come from is popular with social scientists, psychologists, other people who haven't specialized in all the technical details.

My answers to the questions are:

1) All high-level, uniquely human traits (such as being extroverted, liberal, or good at thinking aka intelligent) are best explained by ideas, not genes. There's no gene about extroversion or how to enjoy critical discussion. The knowledge for those traits is in ideas.

2) Humans are not unchangeable, but interventions are sometimes hard b/c *ideas can be entrenched*. Interventions on all issues are possible, and often interventions are *easier for genetic traits* than any of the hard-to-change ideas. If something is really hard to change, that hints it's an idea, b/c ideas are often the hardest thing to change.


Often people argue against nurture by saying "it can't be nurture, b/c i tried to change that aspect of myself and failed". This is quite irrelevant to a correct framing of the issues. There has never been any serious argument that ideas are easy to change, or genetic traits hard; it was just assumed.

Things are hard to change based on how much knowledge there is to prevent change. Ideas can and do often have more knowledge than genes.

Entrenched ideas are hard to change for two big reasons: 1) there is more knowledge behind them to keep them entrenched (b/c memetic evolution goes much faster than genetic, so they are more highly adapted). 2) People use creativity to maintain and defend entrenched ideas (i.e. they create more knowledge). When you try to change a genetic trait, that's a static obstacle, but a memetic trait will sometimes change in the middle of your attempted intervention.

As I like to point out, hair color is genetic but it's not very hard to change it with hair dye. Height is genetic, but it's not very hard to wear platform shoes or stilts. Eye color is genetic, but it's not hard to purchase colored contacts. Having two legs is genetic, but it's not that hard to cut one off, if you want to change your leg quantity. But being a Christian, for example, is a matter of ideas, and for most Christians it's very hard to change.

Another idea people struggle to change is romantic love. Often enough people find their way of falling in love isn't working out very well for their life, but after several broken hearts they still have a very hard time changing it. Some people think this indicates it must be genetic, but that's a bad argument as above. And anyway we know historically that people treated love very differently in other cultures in the past, so how can it be genetic? There's simply a common, unscientific assumption that if people's attempts to change something fail then it must have a substantial genetic component.


I focus mostly on the issue of changing traits because I think that's what most people care about (and indeed it is important).

When it comes to changing traits, the most accurate single sentence would go something like: "It's 100% nurture, but that doesn't mean changing will be easy, you may want to study epistemology, i.e. to learn how to learn, or your attempts to learn new ideas may well be ineffective".

Another single sentence, "Humans are all about ideas, *ideas have consequences* (e.g. determine the course of one's life), and while changing one's mind can be very hard, it's always possible and doing it effectively is one of the most important skills to learn."

Another: "Blaming one's failure to change his mind on genes is a way of abdicating responsibility -- much like blaming a child's disobedience on a physical, genetic, 'mental' illness like ODD -- but in addition to playing the blame-and-victimhood game it's also a way to *give up* and stop trying to improve."

One more: "Nature does not have a 20% influence; percentage is the wrong thing to measure in; it's more of a constant amount, e.g. 20, which doesn't go up as our culture becomes more advanced, but instead becomes trivially small to overcome." (Example: to a low technology culture, changing eye color for a play would seem quite hard. But now it's easy. There was a fixed amount of difficulty which is now beneath us.)

This is not a comprehensive statement. Questions are welcome.

Roy Porter is an expert on the Enlightenment. He has multiple books on it, and made a TV show.

But he doesn't know everything about it. For some issues in his field, he's mistaken.

Porter hinted that Burke was an anti-capitalist, as opposed to Adam Smith. But Porter doesn't know what he's talking about. A story is (it's hard to get really solid info about stuff so old) that Adam Smith said Burke was the one man who thought the same way as him on economic matters. Porter further implied that Burke was an anti-liberal, anti-Enlightenment man, but that's ridiculous: Burke was a lifelong liberal reformer and member of the liberal political party (Whigs).

Porter has Godwin wrong too. He thinks Godwin a hypocrite for his views on marriage and his actions, but he simply does not address Godwin's reasoning. He glosses over the issue quickly, and hopes I'll take his word for it, but I'm not going to, I have an informed view on the matter and Porter offered nothing to change my mind. Porter also makes a factual claim -- with no citation -- about Godwin wanting his daughter and Shelley to marry which I've seen nowhere else (I've read many books specifically on this topic).

Porter is certainly not the only person to get Burke and Godwin wrong. Thomas Sowell has them atrociously wrong, even misquoting them.

These are examples of the simple fact that no expert knows everything, and especially in broad fields there is so much to know that very few people study all of it.

People have holes in their knowledge, even experts.

In my experience with experts, when they speak to an area that I've studied a lot, the majority of the time they get it wrong. They are not usually right, but usually wrong.

Most philosophers have epistemology wrong. It's not just that they disagree with Popper but that they don't understand the issues and address his best arguments. They're outclassed and ignorant.

Most historians of the relevant types have Burke wrong. And most have Godwin wrong.

Popper says most historians of Plato and Aristotle are badly mistaken (and argued his case). He persuaded me. Popper isn't the only one to say this. Godwin had a negative view of them both. Bronowski recognized that Plato's politics were bad. And of course there were Greeks who didn't see eye to eye with Plato or Aristotle (such as, respectively, Pericles and Xenophanes).

These are cherry picked examples. I've simply taken the areas where I know a lot and focussed only on them. Are these same experts right about other stuff where I don't know what I'm talking about? Maybe they are and maybe they aren't, beats me.

Some may reply with arguments that I'm wrong on the examples I've given. So what? First of all for these narrow areas, I'd say I'm an expert. But if you want to think for yourself instead of accepting my expert knowledge, go right ahead. Second, I'd suggest we settle it the way everything should be settled: not by appeal to authority, or consideration of the sources of claims, but simply by critical debate. Post in comments and I'll tell you why you're wrong or I'll concede, simple as that.

Anyway, here's what I think, the lesson to be learned: when I'm in a serious position to judge an expert opinion for myself, I find it lacking the majority of the time. Why should the experts be more reliable for issues I haven't personally studied? I think the experts are simply unreliable all the time, and make mistakes constantly. That makes it all the more important to think for myself, and study important issues for myself.

Genetics and Reductionism by Sahotra Sarkar, pp 12-13:

high [narrow] heritability, which is routinely taken as indicative of the genetic origin of traits, can occur when genes alone do not provide an explanation of the genesis of that trait. To philosophers, at least, this should come as no paradox: good correlatoins need not even provide a hint of what is going on. They need not point to what is sometimes called a "common cause". They need not provide any guide to what should be regarded as the best explanation.

I already knew that. :-)

In Genetics and Reductionism, by Sahotra Sarkar, page 4, he considers what it means for a feature of a person to be genetic. He says that although many people assume it's simple and they understand it, actually it's a tricky problem and presents several unsatisfactory answers and explains their flaws. He doesn't offer the correct answer.

Here's the answer: A feature is genetic if the knowledge for the feature is the person's genes.

This is an example of the general purpose value of epistemology: epistemolgy is needed for solving problems in many other fields.

Let's consider an example. Jack is born and grows up to be a seven foot tall basketball superstar. Is his height genetic? Is his basketball playing genetic?

On both of these questions, some would get confused. They would say the basketball playing is a caused by a "gene-meme interaction" (or "gene-environment interaction"). That is true. Basketball coaches, and parents, are more encouraging to tall children. His cultural environment responds to tallness. And although many would overlook it, becoming tall is not purely genetic but requires environmental help, for example Jack must be fed regularly. The genes alone cannot make Jack tall without the meals.

Some would therefore conclude that both height and basketball skill, and pretty much everything else, are partially genetic.

But let's look at the knowledge. There is no knowledge about basketball in the genes. There is only knowledge about it in coaches, parents, other kids ... in Jack's culture. So basketball playing is not genetic, full stop. Note that this conclusion matches common sense, and also that it can give meaningful answers instead of just vaguely saying everything has multiple causes.

As to height, his parents don't know anything about making Jack tall[1], but his genes do have knowledge about how to construct a tall person. So height is genetic. Again the knowledge-based definition gets the common sense answer.

[1] There are some humans ideas about making people tall. You can stretch them. You can feed them "health food". You can bless them. To the extent the parents do those things — and they work — then the height is partially caused by knowledge in the parents.

Science and Human Values by Jacob Bronowski, pp 60-61

I once told an audience of school-children that the world would never change if they did not contradict their elders. I was chagrined to find next morning that this axiom outraged their parents.

What is wrong with those parents, and how can they be saved from destroying their children's minds?

Science and Human Values by J Bronowski, p 27

there exists a single creative activity, which is displayed alike in the arts and in the sciences. It is wrong to think of science as a mechanical record of facts, and it is wrong to think of the arts as remote and private fancies. What makes each human, what makes them universal, is the stamp of the creative mind.

An Introduction To The Thought Of Karl Popper, p 151, by Roberta Corvi quotes Popper:

the task of the professional philosopher is critically to investigate the things that so many others accept as evident. In fact, quite a lot of such opinions are mere prejudices, uncritically accepted as evident by very often simply false. And to get away from them, perhaps something like a professional philosopher is required, who will take his time to reflect on them critically.

which is from pages 8-9 of Offene Gesellschaft, offenes Universum, Franz Deuticke, Vienna, 1982

So whenever someone says an idea is too obvious for critical debate, too evident to take seriously disagreement about it, too well established to doubt ... well, that's silly. As Popper points out, people take for granted many false ideas, so the fact that it seems really obvious to you is no guide to its truth.

Here is (my summary, my words) the most important idea contributed to Popper's philosophy of science by someone other than Popper. It was contributed by David Deutsch in his book The Fabric of Reality:

Most ideas are criticized and rejected for being bad explanations. This is true even in science where they could be tested. Even most proposed scientific ideas are rejected, without testing, for being bad explanations.

Although tests are valuable, Popper's over-emphasis on testing mischaracterizes science and sets it further apart from philosophy than need be. In both science and abstract philosophy, most criticism revolves around good and bad explanations. It's largely the same epistemology. The possibility of empirical testing in science is a nice bonus, not a necessary part of creating knowledge.

In his book, David Deutsch gives this example: Consider the theory that eating grass cures colds. He says we can reject this theory without testing it.

He's right, isn't he? Should we hire a bunch of sick college students to eat grass? That would be silly. There is no explanation of how grass cures colds, so nothing worth testing. (Non-explanation is a common type of bad explanation!)

Narrow focus on testing -- especially as a substitute for support/justification -- is one of the major ways of misunderstanding Popperian philosophy. Deutsch's improvement shows how its importance is overrated and, besides being true, is better in keeping with the fallibilist spirit of Popper's thought (we don't need something "harder" or "more sciency" or whatever than critical argument!).

Emphasis on explanations is a theme with Deutsch. His upcoming book, The Beginning of Infinity is subtitled "Explanations that transform the world".

Another big idea of Deutsch's is that Popperian epistemology is true for all people. It sounds obvious when stated in that form, but it becomes controversial when one mentions that children are included in "all people". I think Popper would have approved of this, but he didn't go through and explain the consequences and implications for education. Deutsch has done so in detail.

Edit:

In An Introduction To The Thought Of Karl Popper, p 41, Roberta Corvi summarizes Popper, "The practical problem of induction is thereby solved: it is transformed into the problem of testing a theory". This is just the kind of empiricist mistake which Deutsch has improved on. Empirical approaches are insufficient in general because they cannot address philosophy (and epistemology should apply to all knowledge), but even in science when testing is possible, strong empiricism (i.e. we learn primarily using observation) is still a mistake.