Sideways Logic

Thinking in an unorthodox fashion helps broaden the mind.

Posted Mar 03, 2020

If you have not come across the following puzzle, it might strike you as illogical or senseless: A man walks into a bar and asks for a glass of water. The bartender reaches under the counter, takes out a gun, and aims it at the man. The man says thank you and leaves. What happened?

The answer is that the man had the hiccups, requesting a glass of water to get rid of them. The bartender took out a gun instead to scare the man’s hiccups away. It worked and so the man thanked the bartender and left, no longer needing the water.

This is a commonly-used example of what is generally called a lateral thinking puzzle. It is intended to activate unorthodox, nonlinear thinking. We are presented with a seemingly odd situation and asked to explain what happened in a way that remains within the realm of logical possibility. Here is another classic one in this genre:

A truck gets stuck under a low bridge. A group of adults tried to think of some way to force the truck out, without wrecking the truck or the bridge. But they could not come up with a viable solution. A little girl nearby came to their rescue, figuring it out easily. How?

The child suggested that they simply deflate the tires. The term lateral thinking was introduced into education and psychology by Edward De Bono, a Maltese-born British psychologist (although there is some doubt that he was the one who coined the term). De Bono gave the example of the Judgment of Solomon from the Hebrew Bible to illustrate what lateral thinking entailed. Two women came before Solomon, claiming to be the mother of the same child. To resolve the situation, Solomon proposed splitting the child in two halves, giving each woman a half. He knew that the real mother would give up her child to spare her child’s life. And this is what happened. 

It is not a straightforward task to define what lateral thinking is and how it is different from other types of thinking, such as critical thinking, especially since the two types seem to overlap considerably. One way to characterize lateral thinking is that it generates solutions that will appear self-evident only in hindsight.

In contrast to linear logic, lateral thinking is sometimes called sideways logic—an apt metaphor, since we can reach different solutions to the problem at hand from many sides, not just one. This is usually anathema to the puzzle-maker. Nevertheless, this type of puzzle constitutes a fascinating experiment in unorthodox reasoning.

The fifteen puzzles below are paraphrases of classic puzzles in this genre. Keep in mind that there may be more than one answer. Moreover, you might see some of the situations described by the puzzles as unrealistic or flimsy (as I do, by the way). However, as Aristotle aptly put it: “It is the mark of an open mind to be able to entertain a thought without accepting it.”

Puzzles

  1. Non-Colliding Trains! In a small village, the train tracks, as expected, run parallel, except for inside a tunnel where they merge into a single track. One day, a train entered the tunnel going in one direction and another train entered the tunnel going in the opposite direction. Both trains were moving at top speed, yet there was no collision. Why?
  2. Brothers and Sisters! There are seven sisters in the Maroon family. Each sister has a brother, yet there are only eight siblings in total. How is this possible?
  3. The Unusual Elevator! Tilly lives on the top floor of a tall apartment building. He always takes the elevator down to the ground floor to leave the building. Upon returning, though, he can only go half way up in the elevator, needing to use the stairs the rest of the way to the top. Why? 
  4. The Surgeon’s Son! A father and his son were in a serious car accident. The father dies tragically on the scene, but the son survives and is rushed to the hospital. When he arrives, the surgeon exclaims, “I cannot operate on this boy; it is too difficult for me since he is my son!” How can this be, since the father has passed away? 
  5. Consecutive Days!  Without using the words for the days of the week, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday, it is still possible to name three days consecutively. How so?
  6. House Entry Woes!  Marie always takes public transit to work. Yesterday, after a long day at work, Marie arrived home earlier than usual only to find that she could not enter her house, because the door would not open, no matter how many times she turned the knob. What happened?
  7. Polygamy?  A man married fifteen women in his home town over the last six years, but not one of them became his wife. How is this possible?
  8. Lawn Detritus!  Lying on the front lawn of the Garcia family are pieces of coal, a carrot, and a scarf. There is a perfectly logical reason why they should be there. What is it?
  9. Twins?  A woman gave birth to two sons at exactly the same time. But they were not twins. How could this be so?
  10. What Word Is Shorter?  What five letter word becomes shorter when you add two letters to it?
  11. Spelling Conundrum!  What word is always spelled incorrectly?
  12. How Old Is She?  Danielle was born in 1972. She is alive and well today at age 25. How is this possible? 
  13. The Father’s Son!  A doctor and a lawyer were going together to see a movie. One of them was the father of the other’s son. How is possible? 
  14. Dangerous Drink!  Marie was drinking a lemonade yesterday with a straw when all of a sudden she was blinded in one eye. How?
  15. Dangerous Driving!  Jerry was driving down the highway at 65 miles per hour, which was just below the speed limit. He passed three cars going at 70 miles per hour, but he is the one who got pulled over by a police officer and given a ticket. Why?

Answers (There might be others)

  1. They entered the tunnel at different times. 
  2. There is only one brother in the family, who is a brother to each of the seven sisters.
  3. Tilly is very short and can only reach the lower half of the elevator buttons. When he goes down, he can easily reach the bottom button for the ground floor; however, on the way up, he can only reach as far up as the middle button.
  4. The surgeon is his mother. 
  5. Yesterday, today, and tomorrow.
  6. She left her keys at work, and thus could not open the locked door.
  7. He is a priest who married the women to other people. 
  8. They were used to make a snowman. After the snow melted, the pieces of coal, the carrot, and the scarf were all that remained.
  9. They were two of triplets.
  10. Short. If you add the two letters, er, to short (a five-letter word), you get shorter.
  11. Incorrectly. This is how you spell this word.
  12. She was born in a hospital with the room number 1972. 
  13. They were husband and wife.
  14. The straw blinded her inadvertently when she raised the glass to her mouth. 
  15. He was driving the wrong way.