Roger’s version of ‘complexity’ is a common usage, and often the only usage for many IT-folks, in the conventional Aristotelian true/false logic of the _internals_ of most software. But it becomes problematic as soon as we hit complexity in the Cynefin sense, such as in social-complexity or the social/technical interface.

So Roger’s description is not ‘wrong’: it _is_ a good approach to take as long as you’re dealing only with the subset of the context constrained _within_ the IT/software-only boundary – in effect, an idealised if very complicated ‘world’. Just not so good an approach for dealing with the rest of the real-world outside of those rather artificial bounds, where the radically different rules for true complexity (in the Cynefin sense) would apply.

I have found the work of Roger Sessions to be interesting. But as someone who have an interest in systems thinking, complexity science and the Cynefin framework, I have been a bit puzzled as to his definition of complexity.