Kleinberg’s novel measure of causality is intuitive, and she provides several real-world applications of her causal measure, but she might be understating the difficulty of defining causal processes in practice. She says transition probabilities from one event to another can be estimated through repeated observations; however this may be infeasible for many processes that rarely repeat, hindering the applicability of her measure. There is a chapter about token (single occurrence) causality, but her method for estimating token causality relies on knowing the general causal relationships and probabilities.