Fuzzy logic  is an alternative approach to control system design. Fuzzy logic works within the framework of set theory and is better at dealing with ambiguities. For example, three sets may be defined for a sensor: hard failure, soft failure, and no failure. The three sets may overlap and at any given time the sensor may have a degree of membership in each set. The degree of membership in each set can be used to determine what action to take. An algorithmic approach would have to assign a number to the state of the sensor. This could be problematic and not necessarily represent the actual state of the system. In effect, you would be applying a degree of fuzziness.