On what is a priori about necessities

Many have argued that there is something that is a priori about all necessary truths, including a posteriori necessities. According to a particularly popular claim of this kind, one can know a priori whether a sentence is G-necessary, i.e. whether it is either necessarily true or necessarily false. In this paper, I identify the most plausible version of this claim and I argue that it fails. My discussion also reveals, and depends upon, an important feature of putative natural kind terms that has been widely overlooked. I conclude by outlining a proposal of what is really a priori about necessities.