Lewis Carroll’s word ladders, and why they still work
The word ladder was invented by Lewis Carroll, the author of Alice’s Adventures in Wonderland. Carroll came up with it at Christmas in 1877, as a game for two young visitors who had nothing to do, and called it Doublets. In 1879 the magazine Vanity Fair began printing it as a regular puzzle, and it has been in print in one form or another ever since.
The idea is simple enough to explain in one breath: you are given two words of the same length, and you have to turn the first into the second by changing one letter at a time, with every step along the way a real word.
How Doublets worked
Carroll called the two given words a Doublet and the words in between Links. Each link had to differ from the one before it in exactly one letter, in the same position, and it had to be an ordinary dictionary word. Proper names did not count. The fewer links you used, the better your solution.
Carroll’s own example turns HEAD into TAIL:
- HEAD
- HEAL
- TEAL
- TELL
- TALL
- TAIL
Every step changes one letter. HEAD becomes HEAL by changing the last letter, HEAL becomes TEAL by changing the first, and so on down. The puzzles were often set as little stories, such as “Drive PIG into STY” or “Evolve MAN from APE”. One way through the first is PIG, WIG, WAG, WAY, SAY, STY, and one way through the second is APE, APT, OPT, OAT, MAT, MAN.
Why the shortest route is rarely obvious
HEAD and TAIL differ in all four letters, so no ladder between them can be shorter than four steps. Carroll’s takes five, because the third letter changes twice: from A to L in TEAL to TELL, and then from L to I in TALL to TAIL. The detour is there because the direct changes do not all give real words in the order you need them.
That gap between the obvious minimum and the real answer is what makes the puzzle interesting. Changing FOUR into FIVE looks close, since only three letters differ, but a working ladder runs FOUR, FOUL, FOOL, FOOT, FORT, FORE, FIRE, FIVE. That is seven steps, and the last letter passes through L and T before it becomes E.
Vowels are usually where the trouble is. Most English words need at least one vowel, and a word rarely survives having its only vowel swapped for a consonant. So the hard part of a ladder is often finding the moment to change a vowel, and being willing to take a step that seems to go backwards to reach it.
Why the idea has lasted
A word ladder checks itself. You can see at a glance whether a step changes one letter, and anybody with a dictionary can settle whether a word counts. There is no hidden answer to argue about. A puzzle setter also knows how good a solution is, because a shorter ladder is simply better, so the same two words make a fair contest between strangers.
It also needs no equipment at all. Carroll’s version was played on paper, and it works just as well said out loud on a long walk. The puzzle has since gone by other names, including word ladder and word golf, and the golf name fits: there is a par, and every extra step counts against you.
The rules have barely moved in almost a hundred and fifty years. A word ladder printed today is still two words of the same length, joined by real words that each change one letter.
