Introduction

In a number of writings, I have been developing a form of hinge epistemology inspired by Wittgenstein's remarks in On Certainty (1969). The key take-home message is that justification and knowledge—to the extent that knowledge is thought of as, roughly, justified true belief—always take place within a system of assumptions. For instance, for Wittgenstein, it is only by taking for granted that the Earth has existed for a long time that we can consider fossils as bearing on the determination of the specific age of the Earth. If we doubted that the Earth had existed for a long time, we could no longer consider fossils as being evidentially significant for that specific inquiry, since we could no longer take for granted that their formation took place on the Earth throughout a long amount of time. Their presence would then be compatible with alternative hypotheses such that the Earth was created just a little while ago, replete with all the fossils we have found on it, which were created on some other planet or in some sci-fi lab, for instance. Wittgenstein called “hinges” propositions like “The Earth has existed for a very long time,” and thought of them as conditions of evidential significance—that is, as what needs to stay put for the justification of specific empirical propositions to be possible at all. He also had a very wide conception of hinges. In his view, they ranged from very general ones like “The Earth has existed for a very long time,” to more specific ones like “Nobody has ever been on the Moon”; from impersonal ones, like the previous ones, to personal ones, like “This is my hand” and “My name is AC”; and also from universal ones, like “Cats don't grow on trees,” to only contextual ones, like “Here is my hand.” Furthermore, he thought of them as playing a rule-like role not just with respect to the conditions of evidential significance but also of meaningful discourse, including meaningful doubt. Thus, for instance, if one really doubted that there is a hand here (while holding up one's hand in front of one's nose), then it would no longer be clear what one would mean by “hand.” Hinges thus became Wittgenstein's ammunition in stock against various forms of skepticism.