Underlying Assumption

Underlying Assumption

A physical symbol system consists of a set of entities called symbols which are patterns that can occur as components of another entity called an expression. At an instant the system will contain a collection of these symbol structures. In addition the system also contains a collection of processes that operate on expressions to produce other expressions; processes of creation, modification, reproduction and destruction. A physical symbol system is a machine that produces through time an evolving collection of symbol structures. Such a system is machine that produces through time an evolving collection of symbol structures.

Following are the examples of physical systems -

• Formal logic: The symbols are words like "and", "or", "not", "for all x" and so on. The expressions are statements in formal logic which can be true or false. The processes are the rules of logical deduction.

• Algebra: The symbols are "+", "x", "x", "y", "1", "2", "3", etc. The expressions are o equations. The processes are the rules of algebra that allow you to manipulate a mathematical expression and retain its truth.

• A digital computer: The symbols are zeros and ones of computer memory, the processes are the operations of the CPU that change memory.

• Chess: The symbols are the pieces, the processes are the legal chess expressions are the positions of all the pieces on the board

The physical symbol system hypothesis claims that both of these are also examples of physical symbol systems. Intelligent human thoughts are the symbols that are encoded in our brains. The expressions are thoughts. The processes are the mental operations of thinking. In a running artificial intelligence program the symbols are data, the expressions are more data and the processes are programs that manipulate the data.