Lewis Carroll, author of Alice in Wonderland, gave us many examples of what can be said with certainty given syllogisms, such as: No lizards have hair, and no bald creature needs a hairbrush, so no lizard needs a hairbrush. But Carroll also cautioned us against following the form and neglecting content and context, such as the passage of time, giving the false example: The meat I eat is the meat I buy, and the meat I buy is raw, so the meat I eat is raw.
Consider a logic puzzle mentioned by Roy Sorensen: In 1889, Senator John William Harreld married his widow’s sister. Senator Harreld married the sister of the woman who was his wife when he died. How did he do it without dying beforehand? Is it all a terrible legal mistake?
If Harreld married one sister, she died, and then he married the other sister, and he died, he married his widow’s sister before her sister was a widow, which he later made her when he died. The trick is that he did marry his widow’s sister, but not all at once, like the meat in the market. In hindsight, we can say and state truly what no one would or could at either wedding, that Harreld did marry his widow’s sister. If logic is the study of what can be said with certainty, this is a confusing way of saying something logical, something said, stated, argued and believed, but only afterward, as it wouldn’t have been logical to say at the time he married the woman who would be his widow’s sister. If she had known, she might not have married him.