  In late life, Sylvan aimed at enriching the ideas defended in Routley (1980) by developing what he calls “sistology”. On the one hand, sistology adopts all the fundamental ideas of noneism. Like noneism, sistology includes items that do not exist (cf. Sylvan 1991, 837; 1997, 11–12) and it accepts that those items have properties (cf. 1991, 838–39). On the other hand, sistology develops and enriches noneism in the following ways.