This article briefly discusses Hume's original argument concerning the absence of a sensory impression of causation. Hume's argument is important not just because of its historical significance in the debate about the observability of causation, but because it raises issues that arise within that debate in a particularly pure form. The article considers several ways in which psychologists and philosophers have attempted to characterize the sense in which causation might be ‘observable’, and the implications for the viability of a regularity account of causation. It considers whether causation can be experienced in non-visual cases, specifically the experience of touch and the experience of agency. It also considers briefly whether the observability of causation makes trouble for broadly Humean, non-regularity accounts of causation, namely counterfactual, projectivist, and agency theories of causation.