This chapter explores the idea of one variable making a causal contribution to another variable, and how this idea applies to economics. It also explores the related concept of what-if questions in economics. In particular, it contrasts the modular theory of causal contributions and what-if questions (advocated by interventionists) with the ceteris paribus theory (advocated by Jim Heckman and others). It notes a problem with the modular theory raised by Nancy Cartwright. And it notes how, according to the ceteris paribus theory, causal contributions and what-if questions are often indeterminate in economics.