This chapter examines the intelligible and testable kernel of the romantic criticism of the unidirectionality or asymmetry of the causal link. It shows that the limitations of the interaction category, which can by no means be regarded as a substitute of the causation category in every instance. The chapter presents the limitations of causality with regard to reciprocal action, and also shows that functionalism, or interactionism, has in turn severe limitations. The Newtonian law of gravity is usually regarded as an illustration of causality—and even as the paradigm of causality. The inadequacy of asymmetrical causation, as opposed to reciprocal causation, is being acutely felt in contemporary technology, where the concept of feedback as become indispensable, at least in the domain of control. The process that goes on in automatic machines has been called a causal cycle, in contradistinction to linear and one-sided causal series.