Say you're an average medieval Euro-Joe and you want to have sex with your wife. But first, you need to know, IS IT SINFUL? Digging through all those manuscripts of canon law can take forever (plus, as average medieval Euro-Joe, you can't read, anyway). Luckily, James A. Brundage has prepared a handy flow chart for sexual decision making the summarizes the medieval Christian church's take on when sex was OK (Think: In the dark, Mondays, Tuesdays and Thursdays only), and when you were totally going to go to hell.
Unfortunately, I'm not cool enough to figure out how to gank a picture from a Google Books page, so you'll have to follow this link to see the flow chart in all its glory.

And remember kids, it's never ok to have sex if you're impotent! That would be flaunting God's laws of procreation!
http://openlibrary.org/search?ftokens=exbmhralupnz
PS: Great new layout, but I prefer ergonomic black backgrounds over eyestrain-inducing white.
This works really well if you actually decide to sin:
Are you Randy? > yes
Are you married? > no
Stop Sin! > yes (sin, have sex anyways)
Are you in Church? > yes
Stop Sin! > yes (sin, have sex anyways)
Go Ahead! > But be careful, you're still in church, have fun!
Yeah, gun control regulations can be so arcane. And canon law is no picnic either.
s/cannon/canon/
As much as the former is a great typo in this context.
Cannon law blows!
I've posted a jpg of the chart (so you can print it out and display it anywhere you might need to check your Sin Status): http://www.flickr.com/photos/jtropp1/3987102827/in/set-72157608232860732/
How is nudity defined? Do you need to keep on one sock or something?
And is sex allowed to be silly? What if you do it entirely by the book, entirely seriously, try not to enjoy it, etc., but wear a clown wig?
By my quick, back of the envelope calculations, that leaves ~99 days (or, rather, nights) per year when it's OK. Have fun!
We had this posted in the common room of my college dorm a few years back. Always wanted to blow it up to poster size, but an 8.5x11 produced just as much amusement. Thanks for sharing this!
When in doubt - PrtScn+Paste - gank away!
But why WEDNESDAY?! What is so sinful about Wednesday? That puzzles me...
No. Don't have fun. That makes it sinful.
And best hope she doesn't get pregnant, because that's a full (9 months + nursing time) of "Stop! Sin!"
Another helpful link might be this 8/21/2007 Boing Boing post which featured the exact same chart in JPEG form.
Am I the only one who thinks the headline for this piece is a sinful misuse of punctuation?
cjp: Only if you've never watched 70s era game shows.
Wow, I'm amazed that it's ok to have sex while feeling randy.
The chart is much easier to read in Saudi Arabia: Feeling Randy? > Stop! Sin!
The rules of Numberwang are simpler...
-- MrJM
Yawn.
"Oh lookie, see how backwards they were back then?
My, what a nightmare it must have been!
Clearly, we can guess that they weren't free
To break the rules, unlike you or me."
"And best hope she doesn't get pregnant..."
But that amounts to admitting you *were* doing it only for fun! How dare you!
Wait, really? No sex for three days after marriage?? What ever happened to consummating the marriage?
I flipped through the Google book to try and get his sources, but couldn't find any. I guess I'll take it on faith that he has some bit of evidence for it, though, since it's a nice big book and all.