  We are certainly not in a position to resolve this debate here. But it will be helpful to draw a parallel with the debate between the instrumentalist and non-instrumentalist in physics. An extreme form of instrumentalism was advanced by the neo-Kantian Hans Vaihinger in his book The Philosophy of As If (1911). According to this view, the “hard data” of physics consists in the data of our immediate sense impressions. Upon this basis we are free to construct—in common sense and in physics—a “reality”, but the result is not genuine knowledge—rather, it is a useful fiction for moving around in everyday life and making predictions in physics. In a similar fashion, the extreme pluralist takes the “hard data” to consist of the theorems that have actually been established and regards everything else as a useful fiction. 