Conceptual Instability and the New Epistemic Possibility

We tend to think that our concepts are stable in the sense that, whilst their extensions may vary across distinct epistemic scenarios, the reference-fixing conditions by which we discover these extensions remain fixed. This paper challenges this orthodoxy. In particular, it aims to motivate the position that some concepts are unstable in that their reference-fixing conditions themselves vary across distinct epistemic scenarios. Furthermore, it aims to draw out the implications such instability has for epistemic possibility and apriority. I shall argue that when unstable concepts are concerned epistemic space will be widened, which in turn will restrict our a priori knowledge; and in ways that might be salient to solving certain familiar philosophical problems.