Formal Rule

In general terms, a formal rule is an operation or process that can be applied to a symbol or a complex token.  The purpose of the rule is to manipulate the symbol – by moving it to a new location, changing the type of symbol, or erasing the symbol.  The rule is formal in the sense that it can only be applied to certain symbols, and in order to determine if it can be applied, it has to identify the type of symbol by examining its “shape” (or form) (Haugeland, 1985).  For example, the rule for moving a Knight on a chessboard requires that the piece is classified as being a Knight before the rule can be applied.  Formal rules are important to cognitive science in two ways.  First, the classical information processing view basically states that human cognition is the result of applying such rules.  Second, in the specific sense that formal rules are defined in mathematics and logic, these rules can be used to develop proofs at the computational level of analysis.

References:

1. Haugeland, J. (1985). Artificial Intelligence: The Very Idea. Cambridge, MA: MIT Press.

(Added October, 2009)