Author's reply to: David Blockley's discussion of the special issue

Professor Blockley makes a pertinent observation, namely that of the ‘large differences of approach ranging at the extremes from formal (Carmichael) to the informal (Elms)’ within the contributions to the Special Issue. For Civil Engineering Systems to develop as a discipline, it is my belief that some underlying formal structure to knowledge is necessary and this is the thinking behind the BOK Framework proposed in Carmichael (2020). Certainly, not everything can be formalised, individuals will add their informality in any situation, some individuals have an inherent dislike of structure, and many people while maybe clever are not structured thinkers and happily co-exist with shuffled ideas, but an agreed underlying structure will be necessary at some stage in the development of Civil Engineering Systems, as it is in all wellestablished disciplines in engineering. Why not start developing that structure now? Professor Blockley mentions reductionism and emergentism, though the intent of the comments is unclear. Reductionism, to my understanding, attempts an explanation of entire systems in terms of their individual, constituent parts and their interactions. The interactions mean that the whole is not simplistically the sum of the parts. Emergentism, to my understanding, relates to studying systems at their highest level where the properties of the whole are more than the sum of the parts. Systems thinking incorporates reductionism and emergentism as described in the above senses, and this is embodied in the BOK Framework put forward (Carmichael, 2020). Interestingly, the terms reductionism or emergentism appear to be rarely mentioned in any discussion on Civil Engineering Systems, possibly because engineers prefer to explain the relationship between a system and its subsystems in plain terms, unencumbered largely by terms with non-agreed meanings. The historical presence of the terms reductionism and emergentism means that some people lean naturally towards systems-type thinking without any formal education or knowledge in systems. Of course, the terms and practices of reductionism and emergentism can be interpreted in multiple ways.