The recent case law of the CJEU on (joint) controllership: have we lost the purpose of ‘purpose’?

‘Purpose’ is part of the definition of ‘controller’ and a cornerstone of the GDPR. Although the recent case law of the CJEU on (joint) controllership, Wirtschaftsakademie, Jehovan todistajat and Fashion ID, has been much discussed in the legal literature, little has been said about how it relates to ‘purpose’. Therefore, this paper analyses whether, in ruling about (joint) controllership, the Court (sufficiently) took into account the overall nature and functions of the notion of ‘purpose’ in the GDPR.