Our good neighbor, the one who calls us when she sees a bobcat, called us on Friday to ask how our "cat energy" was. She wanted to know if we had seen any bobcats lately. We hadn't since February. She hadn't either. She asked if we wanted to borrow her jade Mayan jaguar carving to put in our south-facing window. She said the first time she had put it in her window her husband spotted a bobcat in their yard a few days later. That was before we had even moved here. I told her I'd be happy to put one of her spirit charms in our window. Why not? It's an innocent flirtation, right? I'd love to see another bobcat. So, I put the jade carving in the window on Friday at sunset.
Post hoc ergo propter hoc -- "after this, therefore because of this" thinking--which is often shortened to simply post hoc, or "If, then therefore, because."
Post hoc is a logical fallacy which assumes or asserts that if one event happens after another, then the first must be the cause of the second. It is a particularly tempting error because temporal sequence is integral to causality — it is true that a cause always happens before its effect. The fallacy lies in coming to a conclusion based only on the order of events, which is not an accurate indicator. That is to say, it is not always true that the first event caused the second event.
The Simpsons (Season 7, "Much Apu About Nothing"). The city had just spent millions of dollars creating a highly sophisticated "Bear Patrol" in response to the sighting of a single bear the week before.
Homer: Not a bear in sight. The "Bear Patrol" is working like a charm!
Lisa: That's specious reasoning, Dad.
Homer: [uncomprehendingly] Thanks, honey.
Lisa: By your logic, I could claim that this rock keeps tigers away.
Homer: Hmm. How does it work?
Lisa: It doesn't work; it's just a stupid rock!
Lisa: But I don't see any tigers around, do you?
Homer: (pause) Lisa, I want to buy your rock.
I called the neighbor to tell her about the bobcat sighting. What else could I do? I know I was adding weight to logical fallacy for her, but I had no choice. It happened. Do I now believe in the power of Mayan jaguar carvings? Of course not. I feel awe-- in watching a shy predator move through the trees, in hearing the call of two eagles during their mating season, in finding a hummingbird at the backdoor waiting for its feeder to be filled. Do I believe these things happen for me specifically--that if I ask nicely, if I put magic in my windows, if I pray chant or cry out the universe will reward me? Nope. I don't. That's why it's awesome that the bobcat walked through our yard. Because it did, and we saw it.
(Definitions of post hoc ergo propter hoc, logical fallacy, magical thinking are from Wikipedia.)