Robotics Reference
In-Depth Information
ple, if we are discussing an object which might (or might not) be a topic
and which might (or might not) be blue, then there are four possibilities:
1. The object is a topic and it is blue
2. The object is a topic and it is not blue
3. The object is not a topic but it is blue
4. The object is not a topic and it is not blue
The process then examines each of these possibilities and eliminates all
those that are not consistent with any information already known about
the object.
Logic machines work by having some sort of physical mechanism for
eliminating the statements that cannot be valid. The mechanisms for
accomplishing this task vary, but they all employ some physical system
for generating all of the theoretically possible different combinations of
the various terms and their negatives (such as our example of the four
listed above). Once all of these combinations have been generated, there
is some physical process, such as pressing a key or punching a lever, which
mechanically eliminates the ones that are inconsistent with any known
facts (the premises).
The Stanhope Demonstrator
The inventor of the world's first real logic machine (one that could solve
problems in formal logic), as opposed to the devices described by Llull
(which could not), was the Englishman Charles Stanhope, the third Earl
of Stanhope (1753-1816). The first version of his logic machine, which
became known as the Stanhope Demonstrator, was built in 1775, and he
consructed a more advanced version two years later.
The Demonstrator consisted of a brass plate, fixed to a block of ma-
hogany, in the center of which there was a square opening or depression.
Two coloured slides made of transparent glass, one red and one gray, were
pushed by the user into slots in the sides of the box. By manipulating the
demonstrator it was possible to show the validity of simple deductive ar-
guments involving two assumptions and a single conclusion. This might
not sound very impressive, but in Stanhope's day logic existed only in the
