## On the Mechanical Performance of Logical Inference in Philosophical Transactions of the Royal Society of London 160, 1870, pp. 497-518 [FIRST PUBLISHED DESCRIPTION OF JEVONS' LOGIC MACHINE OR LOGICAL PIANO]

HANDSOMELY BOUND, FULL VOLUME FIRST EDITION & “FIRST PUBLISHED DESCRIPTION” OF [JEVONS’] LOGIC MACHINE, often called a ‘logical piano’ because of its resemblance to that instrument” (The Origins of Cyberspace, 137). Jevons’ machine was the first logic machine with enough power to solve complicated problems with superhuman speed” – in other words, faster than could a human being.

In 1866, William Stanley Jevons, an English economist and logician, was appointed Professor of Logic and Mental and Moral Philosophy at Owens College, Manchester. As did many other logicians of the 19th century, Jevons wanted to elucidate clear links between mathematics and logic. He was particularly drawn toward developing the ways in which logical problems could be resolved by just repeatedly applying simple, mechanical rules. It was during this time that a principle of reasoning dawned on him that he expressed as follows: “Whatever is true of a thing is true of its like” (Jevons, Elementary Lessons on Logic). The realization galvanized Jevons into action.

Inspired by Boole’s established formal rules of logic and Babbage’s mechanical calculating machine, Jevons was able, in 1870, to take “the last steps towards mechanization of logic deduction” with the machine he devised (Amblard, A Finite State Description of the Earliest Logical Computer, 1).

Jevons began with the hope of constructing “a logical abacus as a device capable of performing logical inference in the way similar to that as the arithmetic abacus is used for calculations” (Stankovic, From Boolean Logic, 74). Basically, he wanted to build a mechanical device that would implement automated deduction – a “labor-saving device that required only the addition of keys, levers, and pulleys to become a logic machine…

“In appearance the machine resembles a miniature upright piano. On the face of the piano are openings through which one can see letters representing the 16 possible combinations of four logical terms and their negatives. The keys at the bottom are used to introduce the terms of a logical equation. This action automatically eliminates from the face of the machine all combinations of terms which are inconsistent with the proposition just fed to the machine. After all premises have been fed to the device, its face is then examined to determine what conclusions can be drawn” (Lee, Computer Pioneers, 401).

The original plans for Jevons’ machine have been lost to history, but this paper is his first description of the construction and is very detailed; it is also accompanied by three copperplate engravings mapping the interior of the machine’s construction. Jevons’ original machine can still be seen today at the Museum of the History of Science, Oxford.

It should be noted that “Jevons’ fame as the inventor of the logic machine has tended to obscure the important role he played in the history of both deductive and inductive logic. He was one of the pioneers of modern symbolic logic) (Lee, 400). Item #640

CONDITION & DETAILS: Philosophical Transactions of the Royal Society of London for the Year 1860, 160, 1861. London: Taylor and Francis, Printers to the Royal Society (11.5 x 9.25 inches; 288 x 231mm). [12], 12, [1], 608, [5]. 52 copperplate engravings. Full volume, complete. Small ex-libris blindstamp and penciled notation on the title page; closed tears at the edges of some pages. Handsomely rebound in aged calf. 5 raised bands at the spine, each gilt-ruled; gilt-tooled fleur de lis at the spine. Red and black, gilt-lettered morocco spine labels. Tightly and solidly bound. New endpapers. Occasional toning and foxing. Very good condition.

Price: \$1,200.00