One meaning of ‘human nature’ is: the set of properties characteristic of, maybe distinctive of, human beings. Human nature in this sense includes many physical properties – having arms and legs but no wings; having two lungs, but only one heart, etc. But it also includes some cognitive and psychological properties – the ability to reason, the ability to acquire language and to understand the minds of others, the need for affection and social connection, and – very probably – a sense of empathy and a sense of fairness. Work by developmental cognitive psychologists indicates that very young children, even infants, display these characteristics long before they could have been taught anything about right and wrong. If so, then empathy and fairness – the psychological building blocks of a moral conscience – are part of human nature.
But why then, do some children grow up to do bad things? Some will say that certain individuals are inherently evil, or evil by nature. This, I contend, makes no sense. Biologically speaking, an individual’s nature is his or her genotype. But genotype doesn’t determine an individual’s observable properties (his or her phenotype) – it only determines what an individual would be like in any particular environment. It is thus nonsense to attribute an individual’s character or behavior entirely to either her “nature” or her “nurture.”
Sometimes we can make sense of the claim that properties are due to our genetic makeup. Some parts of our genotypes produce the same phenotypic property across a large range of environments: for example, almost every human being who survives infancy acquires language. Because these phenotypic properties are so robust, across populations, and across environments, we can conclude that there are some important genotypic commonalities among human beings. Those phenotypic properties can then sensibly be attributed ‘human nature.’
But this is not the pattern with moral properties. There’s not only lots of variation between individuals, but lots of variation within individuals. If we’re being honest, we have to admit that each of us acts virtuously at some times, but viciously at others. And the circumstances that bring forth kindness and generosity from you, might be the very circumstances that provoke harsh words or violence from me. (Consider: affluence can produce magnanimity and generosity, or laziness and a sense of entitlement.)
When the pattern of variation is as complex as this, what we should say about human nature is that the genome supports the potential for both virtue and vice. The psychological findings should give us confidence that we are natively disposed to kindness and justice. The moral challenge for us is to try to discover, empirically, if there are circumstances that encourage those tendencies, and then, if we discover them, to provide them. I’d suggest, for starters: economic security, universal health care, quality education, recreational opportunities, and social respect.