“Historicism” is the view that our values are phenomena of our cultural backgrounds and contexts; and contexts differ from time to time and place to place. Although even the ancient Greeks recognized some degree of moral diversity, true historicism was a discovery of the nineteenth century.
However, modern natural and social science have suggested that some important aspects of psychology are common to all members of homo sapiens, the results of our evolved physical natures. For example, it appears that all people place a higher value on a certain gain than on a probable gain of much greater worth; but they have the opposite view of losses. For related reasons, people will go to great lengths to save $5 on a $10 purchase (?fifty percent off!?), but will not inconvenience themselves to save exactly the same $5 on a $125 purchase. A loss of money reduces happiness more than an equivalent gain increases it.
I mention these findings because we are told that they emerge consistently in studies from around the world; they may reflect mental heuristics that evolved when people were hunter-gatherers. Robert Wright tells us that ?people?s minds were designed to maximize fitness in the world in which those minds evolved,? our ancestral state, which apparently resembles modern life among the !Kung San people of the Kalahari Desert or the Inuit of the Arctic.
However, even if such claims are true, they do not negate the existence of deep diversity in other aspects of psychology and moral judgment. If our physical natures directly determined our answers to all moral questions, then we would not debate ethics or literally wage wars over differences of principle. Besides, many of the features of human psychology that are universal are not moral. Perhaps we evolved to be aggressive toward competitors and altruistic toward relatives. Yet we also have the capacity to limit our aggression and to generalize our altruism beyond family and tribe. People disagree about when aggression is appropriate and in what circumstances one must be altruistic. These differences are especially evident when one compares individuals from long ago or far away. Thus the natural basis of aggression and altruism does not in any way reduce the importance of moral diversity and disagreement.
Finally, the very science that generates findings about human nature is embedded in a particular time and society. This does not mean that truth is inaccessible to science or that its findings are arbitrary. It does mean that we should ask whether the questions and methods of recent science are at least somewhat limited by our local interests and capacities. In sum, Isaiah Berlin was right: ?human beings differ, their values differ, their understanding of the world differs; and some kind of historical or anthropological explanation of why such differences arise is possible, though that explanation may itself to some degree reflect the particular concepts and categories of the particular culture to which these students of this subject belong.?