  The 1970s saw the development and application of the topos concept in many different directions. The very first applications outside algebraic geometry were in set theory, where various independence results were recast in terms of topos (Tierney 1972, Bunge 1974, but also Blass &amp; Scedrov 1989, Blass &amp; Scedrov 1992, Freyd 1980, Mac Lane &amp; Moerdijk 1992, Scedrov 1984). Connections with intuitionistic and, more generally constructive mathematics were noted early on, and toposes are still used to investigate models of various aspects of intuitionism and constructivism (Lambek &amp; Scott 1986, Mac Lane &amp; Moerdijk 1992, Van der Hoeven &amp; Moerdijk 1984a, 1984b, 1984c, Moerdijk 1984, Moerdijk 1995a, Moerdijk 1998, Moerdijk &amp; Palmgren 1997, Moerdijk &amp; Palmgren 2002, Palmgren 2012, Palmgren 2018. For more on the history of topos theory, see McLarty 1992 and Bell 2012).