“…To establish existence criteria for maximal elements of a variable preference relation we exploit the concept of order-completeness borrowed from vector optimization which can be interpreted as a hypothesis on aspiration points recently introduced in the theory of change (see Soubeyran 2009 [23]) or Brezis-Browder's inductivity hypothesis (Brezis and Browder 1976 [8]) when the preference relation is determined by a utility function. Similar to the case of multi-criteria optimization given in Luc [18] and recently in Flores-Bazan et al [11] the method of order-complete sets is very useful in unifying results on existence of maximal elements in various contexts, including (a) existence of maximal elements in social choice theory with non-transitive and incomplete preferences (Bergstrom 1975 [6] for acyclic relations, Tian and Zhou 1993 [25] for transfer upper continuous preferences, Zuanon 2009 [32] for weakly tc-upper semicontinuous acyclic relations, Alcantud 2002 [1] for upper continuous preference on " "-upper compact sets, Andrikopoulos and Zacharias 2009 [3] for consistent upper tc-S-semicontinuous preferences); (b) maximum ordering principles in partially ordered spaces without compactness (Altman 1982 [2], Turinici 1984 [28], Szaz 2007 [24], Zeidler 1986 [30], Zhu and Li 2007 [31] in the context of partial ordering); and (c) efficiency conditions in the framework of generalized multi-criteria optimization (Flores-Bazan et al 2008 [11]). …”