According to Popper we cannot construct foolproof institutions … . The problems of quality of personnel and the need to cope with changing circumstances ensure that constant maintenance is required. It is for this reason that Popper allows himself the admittedly objectionable term “social engineering”. He emphasises that our fallibility imposes on us a responsibility to proceed with care and caution.
Critics concerned about the conservatism of his conclusion have also argued that it is hard to implement: how to differentiate where piecemeal tinkering ends and wholesale alteration begins? Popper admits this difficulty. One obvious difference between the piecemeal and the wholesale is that the piecemeal engineer considers possible unintended consequences of any change carefully and in advance of the change, trying to devise criteria whereby the success or failure of the change can be estimated.