Mind, Body, World- Foundations of Cognitive Science, 2013a

semantic lives, in which they have meanings and symbolic relations to the outside
world. (Haugeland, 1985, p. 100)
Let us briefly consider these two lives. First, we have noted that the rules of a physical
symbol system operate on symbolic components of a whole expression. For this
to occur, all that is required is that a rule identifies a particular physical entity as
being a token or symbol of a particular type. If the symbol is of the right type, then
the rule can act upon it in some prescribed way.
For example, imagine a computer program that is playing chess. For this program,
the “whole expression” is the total arrangement of game pieces on the chess
board at any given time. The program analyzes this expression into its components:
individual tokens on individual squares of the board. The physical characteristics
of each component token can then be used to identify to what symbol class it
belongs: queen, knight, bishop, and so on. Once a token has been classified in this
way, appropriate operations can be applied to it. If a game piece has been identified
as being a “knight,” then only knight moves can be applied to it—the operations that
would move the piece like a bishop cannot be applied, because the token has not
been identified as being of the type “bishop.”
Similar syntactic operations are at the heart of a computing device like a Turing
machine. When the machine head reads a cell on the ticker tape (another example
of componentiality!), it uses the physical markings on the tape to determine that
the cell holds a symbol of a particular type. This identification—in conjunction with
the current physical state of the machine head—is sufficient to determine which
instruction to execute.
To summarize, physical symbol systems are syntactic in the sense that their rules
are applied to symbols that have been identified as being of a particular type on the
basis of their physical shape or form. Because the shape or form of symbols is all that
matters for the operations to be successfully carried out, it is natural to call such
systems formal. Formal operations are sensitive to the shape or form of individual
symbols, and are not sensitive to the semantic content associated with the symbols.
However, it is still the case that formal systems can produce meaningful expressions.
The punched cards of a Jacquard loom only manipulate the positions of
thread-controlling rods. Yet these operations can produce an intricate woven pattern
such as Jacquard’s portrait. The machine head of a Turing machine reads and
writes individual symbols on a ticker tape. Yet these operations permit this device to
provide answers to any computable question. How is it possible for formal systems
to preserve or create semantic content?
In order for the operations of a physical symbol system to be meaningful,
two properties must be true. First, the symbolic structures operated on must have
semantic content. That is, the expressions being manipulated must have some relationship
to states of the external world that permits the expressions to represent
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