•Phosphonates interact strongly with halide perovskites through hydrogen bonds•Deep defect passivation and non-radiative recombination remain unaffected•Shallow point ion immobilization result in high device stability•Nearly 100% of the initial efficiency (21%) is retained after 1,000 h illumination Shallow defects, which are considered benign classical inorganic semiconductors, unfavorably for...

I first summarize Baltag and Smets’ contribution to this volume, and praise their work. Then I compare the anti-lexicographic plausibility update that they propose to a proposal by Aucher, as an illustration of the difference between a qualitative and a quantitive formulation of updates. I quote Spohn’s original work that is at the root of research in plausibility updates and of the notion of a...