 Some writers have interpreted Gödel in this and similar passages pragmatically, attributing to him the view that because empirical statements are paradigmatic of successful reference, reference in the case of abstract concepts should be modelled causally. (See Maddy 1990.) Interpreting reference to abstract objects this way, it is argued, addresses the main difficulty associated with realism, the problem how we can come to have knowledge of abstract objects. Others have argued that Gödel had no paradigm case in mind; that for him both the empirical and the abstract case are either equally problematic, or equally unproblematic. (See Tait 1986.) The latter view is referred to as epistemological parity in van Atten and Kennedy 2003. (See also Kennedy and van Atten 2004.)