 These improvements brought with them an emphasis on formalization (such as Skolem’s isolation of first order logic) and that was for Church a sign that logic was being done; although he no doubt modified his view as the distinction between logic and proper theory became pronounced. Later on, Church himself contributed again to set theory. His paper on set theory with a universal set shows great ingenuity in the analysis of a route to a consistent set theory (consistent relative to ZF) with a universal set (1974c). But he did not think that set theory could handle intensional notions, despite the success of set theoretic model theory for modal logic. For a treatment of intensional notions he continued to look to RTT.