Logic Machines and Diagrams by Martin Gardner

Early graphic representations of mathematical reasoning

For almost a quarter of a century, Martin Gardner (1914–2010) wrote a column in Scientific American magazine entitled Mathematical Games, in which he would present all sorts of math curiosities, puzzles, and brain teasers. These columns were assembled into many collected volumes that were popular with general math-curious readers. He also wrote plenty of books outside of that series on topics concerning math, science, and magic (card tricks and other forms of prestidigitation). Logic Machines and Diagrams, published in 1958, is one of Gardner’s earlier works, written when he had just started with Scientific American. In regards to its particular subject, the book has a sort of master’s-thesis feel to it, but it is still written very accessibly for curious non-mathematicians.

A logic diagram is a graph or chart that helps illustrate or prove the veracity and validity of a series of logical propositions. The most obvious and commonly known example of a logic diagram is the Venn diagram composed of interlocking circles, introduced by English mathematician John Venn in the 1880s. Gardner covers these as well as more complicated forms of logic diagrams. If one takes such diagrams and converts them into a three-dimensional analog—with levers and gears, for instance—then you have a logic machine. The structure of logical propositions can also be translated into electronic circuitry, thus creating an electric logic machine. From there, one naturally progresses to digital logic machines like the precursors to today’s computers. (In 1958 personal computers as we know them today did not exist, but there were giant industrial and military computers like ENIAC.) To solve problems and learn, the “AI” systems that we use today employ the same laws of logic that were explicated by Aristotle, George Boole, and others, just as human brains constantly use these same logical laws without consciously thinking about them.

Perhaps because I’m a graphic designer, the diagrams interested me far more than the machines. I found the first few chapters of this book really fascinating. First, Gardner introduces us to Ramón Lull (or Llull), a 13th century Spanish philosopher who devised a series of complicated diagrams with moving parts in the form of rotating paper wheels. These weren’t so useful for logic, as Gardner points out, but rather they amounted to a sort of Western European I Ching used to inspire philosophical contemplation and intellectual creativity. In Chapter 2, Gardner discusses Venn and other logical diagrammists like him, including the author/mathematician Lewis Carroll of Alice in Wonderland fame. In Chapter 3, Gardner presents his own system of logical diagrams designed to move beyond the computational capabilities of Venn diagrams.

At about the halfway point of the book, Gardner turns his attention to logic machines—mechanical, electronic, and digital. He ends up admitting, however, that none of these machines were as effective as a decent diagramming system, and they amounted to little more than experimental novelties perhaps useful as classroom learning tools. In his final chapter, Gardner speculates about the future of logic machines. Much of what he predicts about computing are things that we now take for granted every day with our desktop computers, tablets, smart phones, and other electronic devices.

For over half a century, Gardner was mathematics’ most charming and prolific ambassador to the general public. The subject matter of Logic Machines and Diagrams isn’t as deliberately fun as Gardner’s Mathematical Games columns, but it will still appeal to the same audience—anyone interested in mathematical “mental floss.”