(I didn't invent this paradox - just re-used it.)

"No no no!", mistress was saying. "Didn't I tell you? Genital shaving and anal exercises by 7 a.m on Sundays. How did I let you get so undisciplined?".

I mumbled something about drawbacks of cellphones as alarm clocks, but basically she was right, as always. A punishment was in order.

You see, mistress is very fair, logical. Sometimes in our discussions, she sees where I am coming from, and rational points do affect her. Not that she is often wrong. Anyway...

"It will be figging and a very soapy enema with a long hold. And you won't know when it is coming - any day from Monday to Friday!".

The not knowing seemed worse. After apologising, I slunk away. Then, I wondered. Could I guess when the enema would be? Were there days she preferred, or which would be more affecting for me?

I took out my IPad, and keyed in:

- mon tue wed thu fri

Hmm.. She couldn't leave it till the last day, because then it would not be unpredictable. I reduced the list to:

- mon tue wed thu

4 days - not so bad. But if she hadn't given me the enema by Wednesday, I would know to expect it on Thursday, so that was out. My list was now:

- mon tue wed

I applied the same logic to Wednesday, giving:

- mon tue

I wasn't sure where this was going, but logic doesn't care. Tuesday had to go as well. The list was now:

- mon

One day on the list. It had to be the one day, so it was completely predictable! The list of days was now empty, and I could avoid the punishment.

I marshalled my thoughts, rehearsed the explanation, and presented the thinking to mistress.

"I see..." she said, after a very long pause. "I understand the logic. Not possible to give you an unpredictable enema, so you don't get one? Well done, but give me 10 minutes." She went into her study.

After precisely 10 minutes, she returned, smiling.

"Clothes off, kneel, butt high!", she said.