 Sober (2001) notes that sea levels in Venice and bread prices in London have both been rising over the past few centuries. Let V represent Venetian sea levels higher than some specified level, and L London bread prices higher than a given mark. If we sample Venetian sea levels and London bread prices over time, we will find that V and L are correlated: In years where V obtains, L tends to obtain as well (since these will tend to be more recent years). However, we have no reason to think that these phenomena share a common cause. They appear to be causally independent.