The biggest myth about engineering design is that it is somehow a ‘rational’ process. David Parnas and Paul Clements begin their now-classic paper ‘A Rational Design Process: How and Why to Fake It’ by claiming that ‘A perfectly rational person is one who always has a good reason for what he does’.¹ That already calls into question the utility of the term, given that there is already a word in ‘rational design process’ that means always doing things for a good reason: ‘design’. Tautology aside, this definition is most notable for what it fails to tell us about the design process. What if there is also a good reason in favour of an alternate—maybe even the opposite—course of action? What if there are good reasons against every available option? How is a ‘rational’ designer to resolve these contradictions?