But perhaps the mathematical fictionalist has a way out. As we saw, Field spells out the notion of conservativeness in terms of a primitive notion of logical consistency: ◊A. And he also indicates that this notion is related to the model-theoretic concept of consistency—in particular, to the formulation of this concept in von Neumann-Bernays-Gödel finitely axiomatizable set theory (NBG). This is done via two principles (Field 1989, p. 108):