The assertion of a cause-and-effect relationship between crime and another variable is often called a proposition, and such propositions are the building blocks of criminological theories. The logic of the scientific method is that theories are advanced by rejecting their alternatives. When the hypothesis that is an alternative to that presented in the proposed theoretical proposition cannot be rejected, then the theory must continue to be developed by adding to it additional propositions that elaborate and test the implications of the theory. This chapter describes the development of a power-control theory of gender and delinquency by this process of elaborating and testing propositions over the course of this chapter. Although the chapter emphasizes the importance of association and sequence, it does not focus on spuriousness. Rather, it emphasizes the role of intervening variables in mediating/transmitting/interpreting and therefore in accounting for causal effects. This is done because the author believes these intervening processes are more common and more important than issues of spuriousness in criminological analysis. Attention is also given to interaction effects that specify conditions under which relationships hold or are modified. These effects can be unstable, often varying across time and place. This instability makes interaction effects interesting, but often frustrating to study. A controversial interaction observed in this chapter involves variation in the relationship between gender, smoking, and perhaps other forms of common delinquency among adolescents in more patriarchal and less patriarchal families. The author is less concerned with the reliability of these findings than with the exposition of the methods involved in their investigation.