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Logical paradoxes are the subject of Viana's column in Folha.

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Reproduction of Marcelo Viana's column in Folha de S. Paulo.

I came across a research paper on logical paradoxes, one of my favorite topics. A paradox is a conclusion imposed on us by reasoning, yet it seems counterintuitive or meaningless. There are countless types, and they have perplexed laypeople and experts alike for millennia.

Many logical paradoxes are linked to some form of self-reference. One of the oldest and most famous is attributed to the philosopher Epimenides, who lived around 600 BC on the island of Crete. He is said to have stated that "The Cretans lie all the time." Since he himself was Cretan, the question remains: is the statement true or false? Be that as it may, it became so famous that it was quoted by none other than the apostle Paul six centuries later, in his epistle to Titus, to explain the difficulties in evangelizing Crete.

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Four other major logical paradoxes are attributed to the philosopher Eubulides, who lived in the 4th century BC in the Greek city of Miletus.

2- The Masked Man Paradox questions what it means to "know" or "be acquainted with." "Do you know this masked man?" one asks. "No," replies the other. "He is your father. Does that mean you don't know your own father?!" It seems silly, but it's not so simple to explain where the problem lies.
3- The Horned Man Paradox plays with the idea that what you haven't lost, you still have. "When did you stop smoking?" they ask. If the answer is "I haven't stopped," what does that mean: that the person is still a smoker, or that they never smoked? The paradox exposes ambiguities of language.

To read the full text, visit the newspaper's website.

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