Why birds can fly: Brought to you by classical logic

By Gordon Rugg

You might already be familiar with the Monty Python scene where one of King Arthur’s knights uses logical reasoning to show why witches and ducks float. As with much of Monty Python, it’s fairly close to something that actually happened.

Here’s Vitruvius, the famous Roman engineer and architect, using the four elements theory (that all things are made of various mixtures of air, fire, water and earth) to explain why birds are able to fly.

Winged creatures have less of the earthy, less moisture, heat in moderation, air in large amount. Being made up, therefore, of the lighter elements, they can more readily soar away into the air.

(From his Ten Books on Architecture)

Disclaimer: If you try using this quote as justification for throwing an alleged witch into a pond, then you’re on your own – this post is tagged under “error”…

Is that handaxe Windows-compatible? The concept of “range of convenience”

By Gordon Rugg

A “Useful concept for the day” article

This is a replica handaxe that I made in my archaeology days. It’s turned out to be invaluable as a demonstration of assorted useful concepts, though I didn’t expect that when I made it.


What would your response be if someone asked you whether that handaxe is Windows-compatible? You’d probably be surprised by the question, because it’s meaningless. As for explaining why it’s meaningless, though, that’s not so immediately obvious.

This is where range of convenience comes in. It’s from George Kelley’s approach to psychology, namely Personal Construct Theory (PCT). It dates from the 1950s, but still has a strong following today because it offers a clean, systematic, rigorous way of modeling how people think. PCT has a rich, well-developed set of concepts for handling language and categorisation and ideas. Range of convenience is one of those concepts.

Continue reading

A very British mystery, part 5: Gavin Finds a Typo

By Gordon Rugg and Gavin Taylor

The story so far: This is a series of articles about the D’Agapeyeff Cipher, a short ciphertext that’s never been cracked. It first appeared in Alexander D’Agapeyeff’s 1939 book Codes and Ciphers. It’s a good testbed for codebreakers who have to deal with short texts. In the previous episodes, we’ve listed the codes described in the book, plus the worked examples that D’Agapeyeff used. In today’s gripping episode, we focus on a typo that Gavin found in Codes and Ciphers. It’s more exciting than it sounds, though admittedly that isn’t the most difficult challenge in the world…

Opening question: Does anyone apart from sad pedants really care about typos, and if they do, is that just a sign that they really ought to get a life?

In fact, a lot of people care a great deal about typos, in a lot of different fields, and for a lot of very good reasons, most of them involving money and the law. They’re also a serious issue if you’re applying for a job. A high proportion of organisations will reject a job application because of a single typo in the covering letter.

So why do people care so much about typos, and what does Gavin’s discovery mean for anyone interested in the D’Agapeyeff Cipher?

Continue reading

A very British mystery, part 4: Quiet bodies

By Gordon Rugg and Gavin Taylor

The story so far: We’re working on the D’Agapeyeff Cipher, a short ciphertext that’s never been cracked. It’s a good testbed for codebreaking methods. In this series of articles, we’re collecting together resources about the Cipher for other researchers. In the previous episode, we looked at the methods that D’Agapeyeff described in the first edition of his book Codes and Ciphers, where the D’Agapyeff Cipher appeared. In this episode, we look at the solutions to the worked examples in the same book, to see what insights they might give.

When you’re trying to crack a code, you look for any clues that might possibly give you some insight into the content of the ciphertext. If you know what the text is about, then you can work backwards from that, and improve your chances of finding a solution. That’s why, for a while in World War II, one of the safest postings for a soldier on either side was in an Afrika Korps forward observation post in the Western Desert (hence the title for this episode).

Continue reading

Hoaxing the Voynich Manuscript, part 3: The hurdle of expert linguist scrutiny

By Gordon Rugg

In this series of articles, we’re imagining that you’ve gone back in time, and that you want to produce the Voynich Manuscript as a hoax to make money.

The first article looked at why a mysterious manuscript would be a good choice of item to hoax. The second article looked at some of the problems involved in hoaxing a text that looked like an unknown language, from the linguistic viewpoint.

We’ll now look at a second set of linguistic problems that you’d face. These problems involve the standard ways that a linguist can try to make sense of an unknown language where there aren’t any related languages that can give any clues.

This is where the text of the Voynich Manuscript starts to look very much unlike any real human language.

voynich repetitive text

Continue reading

Tweet-sized thought for the day: Pattern matching, serial processing, politicians and word salad

Pattern matching is an easy way to check if a thing looks right. Serial processing is a hard way to check if it is right. A big difference. hydeandrugg.wordpress.com

There are two computational mechanisms for solving a problem, regardless of whether you’re a human or a computer. One of these mechanisms is parallel processing, where you carry out lots of tasks at the same time; this mechanism is very good for pattern matching, where you identify patterns (whether physical patterns, or underlying regularities in events, etc). The other mechanism is serial processing, where you do one task at a time; slow, but steady, and much better for catching errors in reasoning.

Humans are very good at pattern matching, which we find swift and easy, and very bad at serial processing, which most of us find slow and painful. So what? So this is why we appear to be an illogical species, and why demagogue politicians can get so far despite having policies that are little more than word salad.

Continue reading