Charles Murray’s review of Thomas Sowell’s “A Conflict of Visions: Ideological Origins of Political Struggles” begins:
One mark of a great book is a thesis so powerful that after a few years people take it for granted. Thomas Sowell’s A Conflict of Visions (1987) is such a book. Its thesis: The policy arguments between liberals and conservatives, socialists and libertarians, do not arise just from differences in priorities regarding freedom, equality, and security. At root, they draw from different conceptions of the nature of man. The Left holds an unconstrained vision: Given the right political and economic arrangements, human beings can be improved, even perfected. Success is defined by what people have the potential of becoming, not by people as they are. The Right holds a constrained vision: People come to society with innate characteristics that cannot be reshaped and must instead be accommodated. Success in political and economic policy must be defined in light of those innate characteristics.
While I tend to think Sowell’s thesis explains a lot for the libertarian/non-libertarian divide, it is not so clear that the left/right divide aligns as well. Both parties use the government to enact their preferred area of concern. It just happens that the traditional Right tends to concern itself with social issues while the Left does so with economic ones.