I have never read any academic research where the interaction between nature and nurture is not taken into consideration in determining the high heritability of intelligence. In behavior genetic studies, very complex nature/nurture interactions are studied and factored into the final results in determining if intelligence is primarily genetic or environmental. It is in fact the Left that refuses to take into account genes when doing research on ways to improve educational attainment for instance-they simply ignore genes and just assume an environmental determinist theory for variation between people and races-making the research highly flawed. Environmental explanations have been so unsuccessful at showing any lasting importance in mental ability that much of the Left's program has turned to simple narrative explanations for why some races do poorly and others succeed. And there is no limit on the number of stories they can produce that inevitably are shown by others, using more scientific methods, to be without any validity.
Barry claims, "I am not aware of a single political philosopher (and I have read a lot of them) who discusses issues involving equal opportunity without assuming that it makes sense to ascribe to each person some measure of 'native ability' or 'native talent', understood as cognitive ability or talent. Some may have doubts about our chances of actually assigning scores for this innate ability, and some think that it is morally insignificant anyway. But they all take it for granted that it is there somewhere. The popular conception of equal opportunity as equal educational inputs to children with the same 'native ability' clearly presupposes the existence of such a thing."
The above is a very confused paragraph, but scientific philosophers HAVE addressed the issue of intelligence, genes, equality, etc. The most thorough denunciation of the Left's position of cognitive equality based on philosophical arguments against psychometricians' methodologies is by Neven Sesardic, where you can find his articles on the Internet or more thoroughly covered in his book Making Sense of Heritability, 2005.
Barry repeats several times that "Anyone who starts with the methodological principle that any differences in ability that cannot be attributed to the environment must be genetic in origin is bound to conclude that the lion's share of the differences arise from genes, simply because we know so little about what features of the environment are relevant and have no way of measuring most of those that we do surmise to be relevant. Genetic determinism, in other words, is simply an expression of ignorance."
Let's break this convoluted and highly specious paragraph down so it is more intelligible. First, any scientist that is either a genetic determinist or an environmental determinist is expressing an ignorance of the scientific method-the statement is propaganda. Second, the components of genes versus environment are always studied together-there is no simplistic "if not E then it must be H" assumption when it comes to assigning variation to genes or environment. Finally, Barry's assertion that environmental variables are too numerous and too difficult to study is baseless. Science is all about testing hypothesis as best one can and repeating those tests to see if they can be sustained. It is part of the research project to find ways to test the various environmental influences that could impact mental ability. After all, the Jensenist theory of a substantial genetic component underlying mental ability has been a 100 year project of successes, but the task was extremely difficult requiring all kinds of new mathematics, disciplines, modeling and creative input to establish the robust results. It is up to the Jensenist detractors to either show why the research is flawed, or produce their own research to challenge the successes in psychometrics in understanding the genetic versus environmental components in mental ability.
Barry asserts, "Defenders of inequality are therefore still faced with the challenge: if people are born equal, how can we justify the enormous inequalities that are common in capitalist countries? The answer is to accept that people are in principle equal in potential, but to attribute inequalities to unequal merits. The rich owe their wealth to hard work, enterprise and frugality, while the poor have a bad moral character, which leads to laziness, fecklessness and the kind of behavior that is liable to land them in prison."
What he is addressing here is the very successful indoctrination of Western societies that people all have equal genetic potential, but there are still inequalities. Conservatives, not being very scientific minded, have generally relied on moral arguments for inequality. However, this position is a political position that does not have any adherents in the scientific fields that study equality. A person's SES, mental ability, personality traits, and some luck all factor into outcomes.
Barry makes some outlandish statements about Herrnstein and Murray's The Bell Curve (1994): "Murray's next foray, The Bell Curve, completed the job and made racism itself respectable, if we take racism to consist in a belief in the genetic inferiority of blacks. This was equally well promoted, equally flawed, refuted with equal thoroughness and - for the same reasons as before - just as successful." I personally read, I believe, all of the books trying to refute the book, and found nothing other than personal attacks on motive, old arguments for equality, etc. The fact is, there was one statistical error that Murray agreed was overlooked, but made no difference on the book's conclusions. But The Bell Curve was not a peer-reviewed academic book in the full sense of the word (though the research articles cited were recognized as reviewed and valid).
What is really egregious about Barry's use of two books by Murray is that he ignores all of the other books that subsequently substantiate what Murray and Herrnstein assert in The Bell Curve. Or he should have cited the primary journal on mental ability-INTELLIGENCE. He just dismisses all of the publications between 1994 and 2005.
He then goes into a sophomoric rage: "The left has one enormous advantage over the right: the case for radical change of the kind advocated in this book can be shown to flow from widely accepted premises without any need to indulge in obfuscation or lies. All that has to be done is to clarify the logical implications of the principles that people maintain they espouse and relate them to the facts. In contrast, the only honest case that can be made for the agenda of the right is that it suits the people who benefit from it very nicely. The left's advantage is offset, however, by the relative sophistication of its ideas [?]. It is not only that they demand institutions that are more complex than those supported by crude pro-marketeers. More significantly in the present context, they also require a more complex understanding of society than do the [untested remedies] of the right. Any fool can comprehend the notion that the rich are rich because of their personal merits, while the poor are poor because of their lack of merit. Of course, only a fool would believe it, but the truth of the matter cannot be conveyed without invoking the concept of a basic structure of society imposing strong constraints on the choices of people located in different positions within it. The power of the ideology that I depicted in the previous chapter cannot be denied. But no more can the inexorable forces that make the continuation of 'business as usual' totally impossible. Scarcely anybody denies the existence of resource depletion, population growth and global warming. But nowhere near so many people are aware of the size of threat they pose or of the scale and rapidity of the response that will be required to prevent the human race from reaching the point of no return. I shall lay out the facts, as I have come to understand them, in the next chapter. These are the basis for well-founded fears, and those who belittle them are liars. But in the chapter that follows, which concludes the book, I shall argue that they provide some reason for hope."
Barry conveniently attacks the conservative right instead of the academic right-those who accept racial and individual inequality in mental ability, etc. Notice also that he claims above, "More significantly [the Left] ... also require a more complex understanding of society...." And yet earlier he claimed that understanding how the environment can increase mental ability was just too complex and that is why the academic Right has stolen the show when it comes to explaining intelligence in terms of genes and development.
In the end, Barry never does produce a theory of social justice that can be empirically tested. It seems the best he could come up with was that people who are less well off feel terribly bad about their situations, and therefore we should make them feel better by redistributing the wealth. In essence, the book is a rambling plea for socialism but never makes a case (nor could it) for its assertions. But that is as it must be, because whether society should adopt egalitarianism or inegalitarianism cannot be answered empirically-it is a personal worldview.