A “multi-magic” square: Each row and column sums to 260; square each term and they sum to 11,180.

“Numero deus impare gaudet [the god delights in odd numbers].” — Virgil

“Why is it that we entertain the belief that for every purpose odd numbers are the most effectual?” — Pliny

“This is the third time; I hope good luck lies in odd numbers. … They say there is divinity in odd numbers, either in nativity, chance, or death.” — Shakespeare, The Merry Wives of Windsor

Before his students arrived for a graduate course in logic, Raymond Smullyan wrote on the blackboard:

PLEASE DO NOT ERASE — BECAUSE IF YOU DO, THOSE WHO COME LATER WON’T KNOW THAT THEY SHOULDN’T ERASE.

Suppose you flip three fair coins.

Necessarily two will match, and it’s an even chance whether the third will be head or tail.

Therefore the chance that all three will match is 1/2.

8589934592 × 116415321826934814453125 = 1000000000000000000000000000000000

Syllogisms offered in Lewis Carroll’s 1896 textbook in symbolic logic:

1. Babies are illogical.
2. Nobody is despised who can manage a crocodile.
3. Illogical persons are despised.
Therefore babies cannot manage crocodiles.

1. No interesting poems are unpopular among people of real taste.
2. No modern poetry is free from affectation.
3. All your poems are on the subject of soap bubbles.
4. No affected poetry is popular among people of taste.
5. Only a modern poem would be on the subject of soap bubbles.
Therefore all your poems are uninteresting.

Raymond Smullyan proposes a scene in which two men are regarding a blackboard. On the board is written ONLY AN IDIOT WOULD BELIEVE THIS SENTENCE.

The first man says, “Do you believe that sentence?”

The second says, “Of course not. Only an idiot would believe that sentence.”

“He clearly does believe it, yet he says he doesn’t believe it,” Smullyan says. “So he’s in the curious position of believing something and also believing that he doesn’t believe it.”

A doubly magic square: Every row and column adds to 840 and multiplies to 2,058,068,231,856,000.