 Only toward the end of that century did a revaluation set in, initiated by Michael Friedman, who took issue, in a series of papers (later collected in Friedman 1999), with the entire English-speaking tradition (going back to Ayer) of seeing the Aufbau as a phenomenalist project of reducing all knowledge to sense impressions on the model of Hume or Mach. Instead, Friedman pointed out, we should see it in the context of its neo-Kantian origins. From that perspective, the Aufbau is better understood as seeking a new basis of scientific objectivity—achieving objective knowledge despite the subjective starting point of individual perception, and the structuralism discussed above  (section 3.2).  On the basis of Friedman’s discussions, many others have since contributed to the revaluation of the Aufbau (Richardson 1998; Mormann 2000; Pincock 2005, 2009; the papers collected in Damböck 2016.)