What matters to the property of metabolism is simply that the binding map implement some ordering on the instances of the material and always choose the minimum under that ordering of the objects that are in pre-goal states. We will return to these issues in section 8 . Other binding maps lead to other kinds of behavior, some of which are pathological. If the binding map always chooses the same binding, then metabolism ceases. If the binding map always chooses uncooked eggs but doesn't impose any ordering on them, it might start cooking an infinite number of eggs without ever actually finishing any one of them.
Metabolism is also an issue for tool use.
To metabolize its materials, must repeatedly reset its tools. An alternate policy is to metabolize the tools too. Let us define to be the binding map that uses not only the leftmost pregoal material but also the leftmost reset tools. Then clearly, is a solution from any state for which is defined. This policy treats tools as disposable .