Post hoc ergo propter hoc
And today's phrase-of-the-month is: Post hoc ergo propter hoc.
I was watching an episode of "The West Wing" on my media center and this phrase was the title of the episode. The literal translation from latin is "After, therefore because of". It refers to the common mistake of assuming that because two things happen in sequence, then one caused the other.
This situation will be all too familiar to the IT Professionals out there. As you know, it is always the last person to touch something who gets the blame for breaking it, or "I installed X and now Y doesn't work, therefore X broke Y". Human intuition has a strong tendency to associate things that happened temporally close together with cause and effect, whereas in fact the two are often not linked at all.
So, IT consultants, if you want to impress (or maybe bamboozle) your customers, next time they tell you that you were the last person to touch their system so you must have broken it, just tell them: Post hoc ergo propter hoc!