For this we use mathematical logic fortified with contexts as objects. Further innovations in logic may be required to treat approximate concepts as flexibly in logic as people do in thought and language. Looked at in sufficient detail, all concepts are approximate, but some are precise enough for a given purpose. McCarthy's weight measured by a scales is precise enough for medical advice, and can be regarded as exact in a theory of medical advice. On the other hand, McCarthy's purposes are approximate enough so that almost any discussion of them is likely to bump against its imprecision and ambiguity.
Many concepts used in common sense reasoning are imprecise.
Here are some questions and issues that arise. Let there be an axiomatic theory in situation calculus in which it can be shown that a sequence of actions will have a certain result. Now suppose that a physical robot is to observe that one block is or is not on another and determine the actions to achieve a goal using situation calculus. It is important that the meanings of used in solving the problem theoretically and that used by the robot correspond well enough so that carrying out a plan physically has the desired effect. We claim The common sense informatic situation often involves concepts which cannot be made precise.