One of the fundamental aspects of cognitive development is the acquisition of causal knowledge. Understanding both formal and folk scientific principles involves appreciating the underlying causal structure of the environment and navigating the inferences that knowledge supports. Adults’ knowledge and reasoning is extremely facile; they make predictions, generate explanations, and reason counterfactually. How do children acquire these causal reasoning capacities and the causal knowledge adults possess? This entry provides a road map of the theoretical landscape for answers to these questions, considers the role of various processes that affect causal reasoning, and examines some specific developmental trajectories, focusing on how they relate to scientific reasoning.