He was Henry the eighth, he was. Henry the eighth, he was, he was.
Did you know that the origin of this tricky idiom goes back to a single member of English royalty? Henry VIII is the one for whom you can blame this phrase. Its first recorded use appears to be a 1539 proclamation of parliament. And yes, it was written “for all intents and purposes,” not “intensive purposes.” As you know, it means “for all practical reasons” or simply “in effect.”
If you were first introduced to this phrase in spoken English rather than written English, I can understand the confusion, but be sure not to sound silly if you use the expression yourself. For all intents and purposes, “intents and purposes” is the way to go.
Got it?