On issues that arise in formulating haecceitism, see Lewis (1986: 220–247), Russell (2013a), Skow (2008, 2011), and Stalnaker (2011). Kaplan (1975) is an importantly early contribution where, among other things, Kaplan attributes the use of the label ‘haecceitism’ to R.M. Adams. On the ways in which Kaplan’s use of ‘haecceitism’ departs from now-standard uses, see Stalnaker (2011: 54–62). For other issues in characterizing haecceitism, see Graff Fara (2009) and Torza (2012).