Espen sez, "I thought you would appreciate this cartoon that explains the difference between covariation and causality. In English, the caption is 'During a convivial gathering there is talk of the unhygienic aspect of using galoshes. One of those present chips in: "Yes, I've also noticed this. Every time I've woken up with my galoshes on, I've had a headache."'"
(Thanks, appliedabstractions)