Proofs in mathematics can be visualized as rewriting strings at each step of the proof upon application of the rules (axioms). This Demonstration shows proofs starting with a hypothesis and positing a goal, represented by the strings "A" and "B", with simple rules of procedure given by string substitution rules. The question answered by this Demonstration is, "If you start at the hypothesis, can you reach the goal using the rules?"
"A" is represented by a light gray cell and "B" is represented by a black cell. The rule icon for the system is displayed above the evolution.