Comparison is the only method for understanding the range of variation in phenomena of a particular type, as well as noting what is common to all of them. 1 It is the first step in theory building. 2 Ideally, in order to achieve this knowledge of the full range of exhibited variation, one should study and compare all known members of a species; 3 but, frequently, that is impractical and one is constrained merely to examine selected members who are known in advance to reveal very different characteristics.
In this search for an underlying structure in modern criminal procedure, I have chosen four modern societies which differ substantially from one another in their cultures and in their political and legal perspectives. Two are "Western" democracies--France and the United States--but, while sharing certain general cultural and legal traditions, they differ from one another in the manner in which cases are processed through the courts, the former using "inquisitorial" methods while the latter uses adversarial methods. 4 The other two--the Soviet Union and the People's Republic of China--share a common political philosophy (Marxist socialism) but have very different cultural traditions and perspectives toward law. Although there has been some borrowing and diffusion, the cultures of all four nations are significantly different although perhaps not as different from one another as they might be from some developing nations of the Third World. 5