A more methodological approach to a critique of systems methodologies came around the same time, in collaboration with Jackson’s colleague at Hull, Paul Keys. Starting from the view that different methodologies were appropriate in different contexts, Jackson and Keys (1984) developed the first version of their System of Systems Methodologies (SOSM). This argued that the way systems methodologies understood problem situations could be classified on two dimensions – one concerned with the nature of systems, running from simple to complex; and the other concerned with the relationship between participants, defined as unitary, pluralist or coercive (in later work, this latter dimension would roughly correspond to hard, soft and critical approaches).