Liberalism believes human nature to be not fixed but changing, with an unlimited or indefinitely large potential for positive (good, progressive) development. This is contrasted with the traditional theological doctrines of Original Sin in which our nature was seen to have a permanent unchanging essence; that we are partly corrupt and limited in our potential. In the late 17th C. John Locke formulated the idea that we are born as tabula rasa (blank slates) and that we learn everything that constitutes our character. Any flaws in our character are therefore the product of our upbringing and environment and therefore subject to amelioration. In the 18th C., Rousseau, Condorcet, Diderot and other French philosophers promoted this view and taught that human beings are innately good, they have un-limited potential, and are perfectible.
Modern liberalism is more cautious: our nature is neither good nor bad; we are "plastic" in the sense that we can develop in almost any direction; there may be some limit to our potential but there is no limit we can specify in advance. As Burnham says, "Modern liberalism...holds that there is nothing intrinsic to the nature of man that makes it impossible for human society to achieve the goals of peace, freedom, justice and well-being".
This outlook is extremely optimistic and one of the reactions we get from liberals when we question an assumption of theirs like this one is that we're being mean and bigoted and trying to spoil things. It has been a tough job during the last 50 years of social science research to propose theories or produce evidence which throws doubt on the tabula rasa belief. One very notable example was E.O. Wilson, who became a figure of hatred for liberals when he published his ground-breaking book Sociobiology. This book explored how natural selection, which undoubtedly shaped animal bodies, had also shaped animal behaviour. That was not controversial but he then went on to suggest that the same processes had shaped human behaviour. He believed there was such a thing as human nature and that it constrains the range of what we can achieve when raising our children or designing new social institutions.
As Jonathan Haidt explains in The Righteous Mind,
Wilson used ethics to illustrate his point. He was a professor at Harvard, along with Lawrence Kohlberg and the philosopher John Rawls, so he was well acquainted with their brand of rationalist theorizing about rights and justice. It seemed clear to Wilson that what the rationalists were really doing was generating clever justifications for moral intuitions that were best explained by evolution. Do people believe in human rights because such rights actually exist, like mathematical truths, sitting on a cosmic shelf next to the Pythagorean theorem just waiting to be discovered by Platonic reasoners? Or do people feel revulsion and sympathy when they read accounts of torture, and then invent a story about universal rights to help justify their feelings?Wilson charged that what the moral philosophers were really doing was fabricating justifications after "consulting the emotive centers" of their own brains.
Obviously, liberals were incensed by this idea and immediately pronounced Wilson to be a "fascist" which justified the charge for some that he was a "racist" which justified that he be stopped from speaking in public. (sound familiar?)
Protesters who tried to disrupt one of his scientific talks rushed the stage and chanted:
"Racist Wilson, you can't hide, we charge you with genocide."This is depressingly familiar behaviour from the liberal guardians of our morals. First the leap from hurt feelings to damning label (fascist); then, on the basis of the first damning label, a leap to the next (racist); then, on the basis of that damning label, he is accused of "genocide"; and then the boycotts, the sit-ins, the campaigns to isolate the heretic and destroy his career and social standing. Such behaviour is reminiscent of witch trials and the Inquisitions. How demonic the angelic liberals can be! But they are in the matrix and they can't see themselves for what they are.
The research by Tajfel on minimal groups points to something in human nature which is both very deep-seated and unchangeable. We coalesce into groups very readily and on the basis of our group membership we make judgements about the superiority of our own group. We even do this when the group we are assigned to is based on trivial, arbitrary, and random criteria.
Confirmation bias is another universal in psychological research. We are very good at finding and remembering information which confirms our beliefs but absolutely terrible at seeking or remembering information which contradicts them. This behaviour is found across all cultures, it is not limited to the New York Times. We are cognitive misers who find the quickest route to the conclusions we want to reach and we apply different tests to information depending on whether it supports our beliefs or contradicts them: for the former we ask Can I believe it? and for the latter we ask Must I believe it? We are biased by nature. We also continue to cling to beliefs even when presented with strong evidence that those beliefs are false. Liberals will read this and continue to believe that human nature is perfectible - given the right social conditions.
One of the things that has made science so successful is that the scientific method is a procedure which enables us to circumvent the natural human tendency to seek information confirming our beliefs. In science, we can formulate a hypothesis which is a clear statement about the world that can be subjected to a confirming or falsifying test (a falsifiable hypothesis may be preferable). The test can be designed so that it is a fair and objective test of the hypothesis. Arriving at a conclusive true or false test is obviously much easier with respect to physical phenomena than it is with psychological and social questions and there is therefore much less wiggle room when results contradict a pet belief. Many scientific facts are neither pleasant nor unpleasant to know; they are simply useful. When they do have more emotional impact they become controversial and hotly contested - think of evolution for example.
Psychological and social information does generally have an emotional impact; there is a basic like or dislike response to it. This necessarily engages the mechanism of affective priming and the powerful forces of the emotional centers of our brains. Try as you might, you cannot prevent this. (The liberals attacking Wilson certainly didn't even try.)
Moral Foundations Theory indicates that we are born with a number of inherited moral foundations. These moral foundations are the result of evolution. Different cultures (and social environments) develop these structures in different ways and to different degrees. Nevertheless it is these moral foundations which underlie moral responses in all of us, they are part of our nature.
These examples should be sufficient to show that human nature is not infinitely malleable nor inherently good or perfectible. Liberals will look for flaws in the arguments that will enable them to wriggle off the hook of Must I believe it? I can't do anything about that, it's just human nature.