Cause, effect, efficiency and soft systems models

The logical connectives in the conceptual models of Soft Systems Methodology are limited to relations of ‘necessity’. This is not enough to achieve a correspondence with states of affairs in the physical world. In order to attain this correspondence connectives representing ‘sufficiency’ must be included. When this is done a logical account of efficiency is possible. This defines efficiency as the arbiter between two or more sufficient but unnecessary conditions of a desired effect.