Caveat Emptor – let the buyer beware. Good advice for almost anything from buying cars or houses or making investments and, for that matter, in trying to make sense out of the nature–nurture debates. As is true about anything within the academic disciplines, the nature–nurture debates rest on certain basic assumptions about theory, methodology, and analysis. What is the subject matter? How is it defined and measured? How are data collected? How are they analyzed? How are they interpreted? These are not, in fact, questions unique to the nature–nurture debates but rather are generic to all aspects of the study of human development. Nevertheless, the nature–nurture debates often serve as the primary battleground for skirmishes between opposing sides on each of these issues. It is in this sense that I define one of the nature–nurture debates as the “proxy debate.”

This chapter is mostly about the proxy debate because it is these questions and assumptions on which they rest that speak to the heart and soul of human development as a discipline. These questions and assumptions can perhaps best be grouped together in two, admittedly overlapping, broad categories. The first refers to issues related to the question of the most appropriate level of analysis one should use in the study of human development, and it is this issue that serves to differentiate the classic debate from, for the most part, the new debate. The second broad category relates to a host of issues concerning research design and analysis, and it is this issue that most often serves to put the two sides of the classic debate at odds with each other.