In multiple publications over 3 decades, most recently in The Book of Why, Judea Pearl has led what he regards as the ‘causal revolution’. His central contention is that, prior to it, no discipline had produced a rigorous ‘scientific’ way of making the causal inferences from observational data necessary for policy and decision making. The concentration on the statistical processing of data, outputting frequencies or probabilities, had proceeded without adequately acknowledging that this statistical processing is operating, not only on a particular set of data, but on a set of causal assumptions about that data, often unarticulated and unanalysed. He argues that the arrival of the directed acyclic graph (DAG), a ‘language of causation’ has enabled this fundamental weakness to be remedied. We outline the DAG approach to the extent necessary to make the key point, captured in this paper’s title regarding DAG’s potential contribution to improved decision or policy making.