 Mackie’s regularity theory of causation still fails to distinguish between genuine causes and mere joint effects of a common cause. To see this, consider an example adapted from Russell (1921 [1961: 289]): the sounding of factory hooters in Manchester is regularly followed by London workers leaving their work. And yet the former is not a cause of the latter. However, as Mackie (1974: 81–84) himself points out, the sounding of the hooters in Manchester counts as a cause for the workers going home in London: