Igualdade, liberdade e a natureza humana Steven Pinker, no seu "The Blank Slate: The Modern Denial of Human Nature" diz que:

A nonblank slate means that a tradeoff between freedom and material equality is inherent to all political systems. The major political philosophies can be defined by how they deal with the tradeof. The Social Darwinist right places no value on equality; the totalitarian left places no value on freedom. The Rawlsian left sacrifices some freedom for equality; the libertarian right sacrifices some equality for freedom. While reasonable people may disagree about the best tradeoff, it is unreasonable to pretend there is no tradeoff. And that in turn means that any discovery of innate differences among individuals is not forbidden knowledge to be suppressed but information that might help us decide on these tradeoffs in an intelligent and humane manner.

Uma excelente síntese do que separa a esquerda da direita e das razões normalmente aduzidas para a negação da natureza humana e das diferenças inatas entre indivíduos.